It still doesn't work entirely as it should, that's for sure.
I played Mass Effect Legendary Edition last night, and it was the only game to show up in my collection at the time, with The Sims 4 nowhere to be seen. Restarted the EA App to see if that would fix it, but instead, MELE disappeared as well and my collection was suddenly completely empty. This morning, all games were back again.
Now that I know it's just a bug and my games don't actually go anywhere when I can't see them, I'm okay with just restarting the PC to make them reappear. But of course, I hope this bug will be addressed in the long run.