Uploaded my set of > 4000 custom songs to the Quest 3 yesterday. Game took its time scanning the files, but that’s expected (and only happens once anyway).
Once it was done, all seemed fines, the songs were findable and playable.
However, there was a 5-10 second loading time both to get into a song stage and to get back to the menu afterwards. This was my first time playing with the new update so I assumed it was just an unfortunate side effect of that.
However, today those load times were gone and everything was as snappy as I remembered it being, so it was more likely caused by the custom song load (memory fragmentation?) - perhaps the game could pop up a message recommending restarting the game after loading more than N songs (not sure what N should be though; 500? 1000? 250?)