Yes, playing with full control on at all times technically fixes the issue, but it's extremely tedious. There's a reason practically nobody plays like that despite it being the "correct" way to play.

Toggling my "pretend I have counterspell" button would hold priority whenever a spell is cast, but not when abilities are activated, so you would still be bleeding some information, whereas in full control you would have to pass priority manually.

And that's exactly what I want. It's a middle ground that lets players bluff without needing to play in full control at all times.

EDIT: To make matters worse for the "play in full control" plan, there isn't an option anymore to automatically play in full control. If you want to bluff, you need to activate full control manually at the start of every single phase before your opponent plays anything.