Let's deal with the elephant in the room, which is that there are two reasons this topic is coming up: first, because people are worried about the Akatsuki "suddenly" having anti-SC / anti-summon technology and second because there is a sense that Hazō should have had access to these things all this time, either in Jiraiya's hoard or through general access to Leaf's tech.
I agree that the proposed countermeasure as described is something that's reasonable for the Akatsuki to have. That said, I would argue that from the playerbase's previous epistemic position, it was eminently reasonable to assume that the Akatsuki are going to be given a setting-changing seal "array" that could create a runic-tier effect capable of instantly dispelling all summons on a wide are.
This was, after all, what was initially suggested that they did:
(Major point) Akatsuki knew that they were likely to face off against summons and prepared countermeasures. The Nagi Island report states: "Although the Leaf contingent had a large number of summons with them, when they reached the battlefield all of the summons popped at a specific point, as though they had run into a brick wall. Jiraiya was able to quickly re-summon Ma and Pa but no other summoner was able to duplicate the feat." Hazō doesn't know for certain how this was done, but since he is one of the few people who know that summons' chakra envelopes are made of nature chakra he can infer that Akatsuki invented a seal array that pushes nature chakra from a large area and generates a bubble that prevents it from flowing back in. If Jiraiya had nature chakra in his body then perhaps he was able to use it to re-summon Ma and Pa. Hazō does not know why Jiraiya did not summon Gamabunta in addition to / instead of Ma and Pa. (Note: we normally prefer not to have Hazō do all the deduction work for you; we are offering it in this case as a gesture of good faith and part of our apology.)
This implied that the QMs had a model of seal "arrays" whose capabilities are permitted to be orders of magnitude bigger than those of "normal" seals and multi-element seals; capabilities on par with runes. If this were part of the setting, I argue it
would be completely unreasonable for Hazou to never hear about a dramatically powerful seal "array" useful against, say, the Dragons, and to never consider creating a given seal effect using a seal "array".
In addition, if it
were implemented as stated in the second quote, it
would have read as the Akatsuki being randomly given a setting-changing capability as a hasty last-minute patch to a years-old mistake. If such countermeasures were easily possible, everyone would have had them, or something on their scale. That everyone doesn't have them implies they are not easy to develop: something requiring the focused attention of an S-rank sealmaster over a prolonged period, and/or esoteric knowledge. It's reasonable that the Akatsuki could have it; it's not reasonable that they're given this as a last-minute patch to a years-old mistake. As far as shenanigans go, it'd be on the order of initially modeling Hidan as an essie-on-stats-alone, and then suddenly retconning him to have regenerative immortality because he wasn't supposed to die this chapter.
The second quote implied that you thought both were reasonable: that it was reasonable for seal "arrays" to have such capabilities without Hazou knowing about them, and that it was reasonable to grant the Akatsuki this tier of capability at no charge. (If it were initially presented as "Hazou infers the Akatsuki scattered deals-one-stress seals all over the battlefield", I legitimately expect there would've been much less drama.)
Therefore, it was not unreasonable for the players to expect the QMs to do that. It wasn't a baseless expectation that you'd act in bad faith, it was an expectation that you'd proceed to do what you, in fact, stated that you considered reasonable to do.
Edit: To restate, I have no issues with what's being suggested now. But I do end up having the impression that if the players did
not generate enough salt to make it inconvenient, the QMs
would have proceeded with the changes which the QMs are now calling it "assuming bad faith" to expect them to implement.
