I agree with the user on this one. I'm a big fan of the playlists that are curated by Spotify, and I like how they are sometimes updated with new music. It's unfortunate then that I have to copy the songs into a static private playlist to disable the crossfade, because I'd have to do that every time that the real playlist receives updates.
It's unclear why the on/off switch to crossfade music in the preferences doesn't affect these playlists, so I'd call that out as a bad user experience. If I disable crossfading in my preferences, then I'd assume I won't have crossfading in any and all of my playlists, private or public.