It stayed at that high number for months though, despite periodically launching the game.

So, it usually does. But I went to check again. It had me for 63 hours of Baldur’s Gate 3 which I remembered was very off. I launched the game to check the in-game count : 19 hours. I exited the game, and lo and behold, Steam now says 16.8 hours.

I give it a B+ for effort.

Not to undercut it, but the steam deck shows triple the actual game time for some of my games, as it probably counted the time the device was asleep with a game running, due to some glitch.