In Apple Music, they are just greyed out. If you own the album (have it in your library, or have it match to cloud library) it will be playable. The "Album Only" tag is only in iTunes music store, which is different than the Apple Music catalog.
For lack of a better example, the Les Miserables Complete Symphonic Recording has the first track greyed out in the AM catalog. In iTunes, it is labeled as "Album Only" in the Price column. This album is in my library from a CD rip, which then I "matched" to my iCloud Music library. The first track is available for play for me.
Likewise Adele's 25 album, which is not even listed in AM catalog. I matched it from a CD rip into my iCloud music library. I can now stream it from any of my devices using AM.