Judging by what OP is describing this isn't a bug, it's a functionality change they thought was better. And they might even be right for the majority of users. But OP has a valid use case that's broken by the change.
Yea, the problem is Apple thought this was an UI improvement, but actually broke a common usage pattern. This kind of change should definitely be a setting, and considered thoroghly before changing the default. This is poor design and lack of QA, not a bug, per se. But the result is even worse because it means the previous functionality likely isn't coming back.
Definitely a failing of understanding how real people use the software here. Frustratingly, Apple has a tendency to dismiss users who have different intentions than the product manager thinks they “should” have. Even if most users would want a certain behavior, they are “courageous” enough to tell users they’re all wrong and they should use it a different way. Funnily enough, the infamous Apple discussions forum features volunteers who consistently have that same attitude. Fans who have internalized the Apple “we know best” principle.
So I also wouldn’t bet on the feature coming back.
It's a trade-off. It could be a setting, but if one adds too many settings then the space of possible options gets huge and bloated leading to bugs and complexity for the users and I already barely know how to use iPadOS.
"If you ask a user what percentage of Word features they use, they will tell you 10%. But if you ask multiple users which 10% they use, they will all give you a different 10%."
Except in this case it's within reasonable expectations that starting airplay from within an app will only project the app's content and not your whole screen or other apps
