I don't see them visible on my profile, as of now, but my profile also doesn't seem to be loading reliably.
I can confirm that private playlists are accessible by their link even in an incognito window. That is surprising to me. Has that always been the case?
edit: a quick google suggests that sharing by link is known to allow access to anyone with the link.
Someone posted about it the other thread for the same news.
I am shocked.