Sage Mode is exclusive to the incredibly talented. If you mess up your meditation while learning it even once, you get permanently turned into a statue for reasons. Also, there must be other unstated requirements, since Orochimaru had access to it but was explicitly unable to learn it for physiological reasons.
Yeah, there are definitely reasons why not every summon-taught technique can be passed on to just anyone. In the case of Sage mode it is pretty obvious but it's not farfetched to come up with reasons for other techniques as well. Maybe having access to PC would only have been possible for Keiko because she shared blood with their summons and outright impossible to teach to anyone not tied as directly to pangolins as her.
Anyway, to get this back on track from where we started: Just because we are able to learn an armor technique does not automatically mean every single summoner will be able to learn the same or equivalent technique because:
- there could be (physiological) restrictions like Sage mode like you mentioned above
- the summoning clan does not want to share their secrets and you haven't offered anything of value (like Skytowers) to convince them otherwise; this could lead to only seeing proven and already skilled people like S-Ranks or top jonins being taught techniques at best, with Chunin level ninjas like Keiko being the super rare exceptions because her contribution to pangolins was not based on combat prowess but ingenuity of her team and the hivemind
- the jutsu takes too long to learn before it offers acceptable benefits (like Ghost Scales right now) so you would only find them on very high end ninjas or not at all (because the summoner died before he could get the jutsu to work properly, see
@MadScientist's post about how leveling GS right now completely gimps our other stats)
- not every summoning clan was created equal; some may have more or less compatible jutsus that they are able to share with their summoners
- they can share with you but specialize on one specific thing that you cannot use; again the Sage mode comes to mind, super powerful and much better than Ghost Scales but if you are not able to learn that then the Toad clan might not be able to offer you anything else because all of their techniques build upon Sage mode. Other summoning clans might not have That One Powerful Thing but multiple and varied jutsus like we are seeing from the pangolins
There are many ways to defeat someone. Surprise attacks. Traps. Poison. Techniques that do unexpected things just when you thought you were winning. You certainly don't have to capture them - scrolls are indestructible by normal means, so you could happily drop a chakra nuke on a summoner and pull the scroll out of a pile of ash.
The point was torturing the information out of the summoner him/herself and I still stand by what I said about carrying a tiny summon with you to reverse summon you whenever you are in danger (or kill you if you are 100% certain to get captured if that is something you agreed to beforehand). For the scroll, just keep it stored somewhere else.
And Kagome might throw a proper fit at me even thinking this: But suicide seals on our person should be a thing. Seals that will explode and kill you unless you do activate them every x minutes.
Also, and feel free to correct me if I'm misremembering, summon scrolls themselves cannot make the journey to the Seventh Path, meaning you don't want to be reverse-summoned from combat except as an absolute last resort. If this were not the case, every summoner would store their scroll on the Seventh Path. That would make them immune to theft altogether, but but also mean that if the summoner died, the scroll would be stuck on the Seventh Path unless the clan was willing to hand it over to another clan to take to the human world.
I don't remember offhand if I saw a scene with Jiraiya and/or Naruto together in the summoning realm with the summoning scroll being openly visible on the floor or similar, though going by Occam's Razor: Where else would the scroll have been if not on their person? Canon definitely never went out of their way to show us that the scroll was put into a secure location before Naruto got summoned for his Sage training for example (though one could argue that Kishimoto just never even thought about it one way or another). The smart way would be to store it in a secure location obviously but since we are looking at canon...
And besides, there was also some toad who was basically a living scroll (the key to unlock Kurama's prison or something so it was a proper and working seal) who could leave and enter the summoning realm at will.
Further, browsing through the wiki, Jiraiya is usually seen with a huge scroll that looks like
this which suspiciously looks like the
summoning contract scroll.
But yeah, basically this is something where I think QMs can decide either way and it would be fine. Either way, there are ways around the limitation by just storing them some place else and not on person.
There's always the argument that you should only teach it to the likes of Naruto, because they can leverage it to its full potential and having a low number of high-power users will stop it spreading to other villages. It avoids cases like Kakashi, who hardly ever uses the technique because of how hard it hits his chakra, yet could still give it up under torture.
I think the plan was to make a farm out of chakra beasts for Noburi to drain at will and only use the Shadow Clone inside clan grounds in a secure location (preferably with anti-Byakugan seals) where Noburi could supercharge all of us for a single clone each, never to be used out of combat so it should remain a secret. For gameplay reasons this could offer XP discounts on training or accelerated seal research and so on.
Or the likes of Noburi?
If you need insane chakra pools to use it, he's got that covered. Did you know he only needs 238XP to hit a thousand chakra points?
I'd be wary of letting Noburi use this in combat when we could just focus on the Water Clone for him. Shadow Clone's main advantages are scouting and being able to accelerate training. For combat use, Water Clone should be able to do anything Noburi would want them too, right? Neither clone can use his blood line after all so the obvious strategy of doubling the drain rate on people caught in Mist and doubling the recharge rate of his allies wouldn't work anyway.
EDIT:
At the risk of turning into
@eaglejarl: I want punching and I want it tomorrow. Think of Lee and how disappointed he must be to go weeks between punching.
)
