You know you can turn that off, right? You can turn off activity sharing in activity privacy, and then when you've opened the game and it's in your registered games list, you can go into your settings and toggle detection off for that specific game. I for one always have activity sharing off whenever I play a game like this, so this is 100% a you problem.
because, yes, i like to manually toggle things off, then back on again.
However the problem lies in the fact that this is even possible for it to automatically detect like this. so far as i remember setting things up, only games i play though steam should even be recognized by discord in the first place.
rich discord presence should be an optional toggle, and be off by default.