I will reiterate: Apple Music is not automatically deleting tracks out of your Mac’s library, nor is it trying to force you to stay subscribed to the service. In this instance, it appears that Apple Music is an unfortunate scapegoat: The real problem may be a bug with the subscription service’s container application, iTunes.
Based on several Apple Support threads, it appears that the most recent version of iTunes 12.3.3 contains a database error that affects a small number of users, and can potentially wipe out their music collection after the update. The error has been mentioned a few times, primarily on the Windows side, in the weeks since the 12.3.3 update, but appears to be rare enough that it hasn’t previously received major press. Apple did put out a support document shortly after the 12.3.3 update that walks you through some fixes if you find that your local copies of music are missing.
I knew the panic last week was BS.