This is incorrect.

It’s still dependent on the OS it runs on AND the SDK it compiles against (not the OS it was was compiled on).

But that is legacy bridging behaviour, and is not compiled into the app. Apple can and do change those with time.

For example apps that compile against macOS 15 are not opted into Liquid Glass when run on macOS 26 but will be once on macOS 27 according to their transition docs.

That doesn’t really negate the OPs point.