The problem here, I think, is people who doesn’t speak from experiences but goes by with what they read and let their confirmation bias dictates what they read and remember.
I *am* speaking from experience. As I said, three attempts. The first was the free trial when the service debuted, the second was the following year, the third was last year. Each time allowing Apple Music access to the local library resulted in tracks randomly being replaced with other tracks, random duplicate tracks (tracks that should have matched, but did not), and tracks just disappearing (removing the library track outright in favor of the AM track).
There is zero reason for Apple to require the subscriber to allow access to the local library even for something as simple as making a playlist. Why they do that, I have no idea.