@Reed meanwhile, 13 years later... but thought I'd chime in anyways. Not sure if you happen to have a rooted phone, but if you do, I'm guessing this is possible since 2019 with the LSPosed Framework. It should allow you to create code that can intercept the other app's calls to its onAttachedToWindow(), add the flag and continue the flow.

Beware: this will take you down a rabbit-hole involving diving deeply into Magisk, LSPosed, and most likely having to take steps so your banking apps, wallets, netflix, etc do not detect root. It depends on how badly you want this and you having a significant dose of grit 😜 #GoodLuck!