It seems that the way that YTM maintains playlist is by keeping a track list and populating it on the fly with the first hit it gets. If the metadata doesn’t include a special mention of “explicit” or “clean”, you end up with a crapshoot on which version you’ll get.

For me it even went beyond that. I had uploaded my personal collection to Play Music. When they migrated to YouTube Music they replaced my tracks with tracks from their catalog, including edited versions.