Let's keep something in mind; this is a battlemagic spell.
This is not an "instant distraction" spell. This is not a good "make a distracting body double spell". This is not a spell you use when you want to sneak away and distract somebody; this is a spell you use when you want to send out a cavalry rider to kill a target.
So saying "we'll often want enemies to think it's Mathilde" is inaccurate, because we won't "often" use it at all, as it is battlemagic. And when we do use it, its primary usage will be to hunt down a target and kill it.
It can be used as a distraction or for confusion. But if you're doing that, or wanting that, then it's still not that great a distraction ultimately; because once they start fighting it, they'll notice it doesn't act like Mathilde, and if they stab it and it bleeds shadow or Aetheric Vitade instead of blood, or if it doesn't fight back with spells, or if its blade doesn't have the characteristics "screw everything I hit with this" effect of Branulhune? Or if it gets stabbed and disperses? Yeah, it's gonna be kind of a giveaway.
And if you wanted to use it as a distraction by placing it in a location and telling it to go off elsewhere rather than fighting, to lead people on a chase? Then you're using battlemagic to make a distraction instead of killing. In which case, maybe you would have been better off using Illusion to cast that; or using Doppelganger on yourself to avoid notice and sneak away.
There's also another possible issue here; namely, what if you did want to use a Rider in Red as a distraction... but you didn't want it to be mistaken for Mathilde?
Because that, too, is a possible viable use of an Apparition -- if you were going to use it for distractions or feints rather than to fight -- and which would work well if it had a weird or generic appearance, rather than a specific appearance of a specific person.
i.e. The ability to make it appear like Mathilde is kind of a very niche thing. If you're using a battlemagic spell as a distraction, it can probably work as a normal distraction too. You can also just be stealthy on your own, rather than using a tricky Apparition for it.
Making it look like Mathilde is mostly about being cheeky or wanting to do the Dammerlichtreiter legend, rather than about tactical utility, I feel like. It might be cool or neat, and that might be a reason for people to do it. But I think trying to sell it as "think of the common tactical applications" is wrong. Because that will not be a common tactical application.
