the album is only uploaded to spotify when the label company wants it to be on spotify, so my best guess is they are letting it stay off spotify for a while (hours or weeks, however long they decide) to help promote sales on other platforms (Ex: Itunes Store)
Sadly all the streaming services have resorted to this advertising type tactic. You can find some artists music at only certain services. Prince moved all his streaming content to Tidal. Dead Kennedys material is still not fully available at Spotify, only a few select songs on some releases for U.S. listeners are currently available. Spotify has exclusive artists content to stream from Pink Floyd and Rammstein for examples. It is not surprising Apple has pulled this same thing, being that The Beatles material is exclusive to the iTunes store only for digital download sales, which is sad being that a good chunk of The Beatles material is over 50 years old now. If the Stones can put their music up on streaming services, do not see why The Beatles can not do so as well? Some of the content being recorded from the late 50's, from the beginnings of the Rock 'n' Roll hey day from the 50's, the reason Pandora is arguing for public domain use on some older Beatles content and other artists output from this period. Google has just now been able to put some limited Beatles content up on their radio station system. Should not be too much longer before monopoly type tactics with regards to music are no more, streaming has opened the doors it is only a matter of time when the same material on one system is available on all services, and then things will come down to app options and the overall functionality of the service for the users. Better get them bugs worked out.
The Apple exclusive thing was probably just for the initial release to bring some buzz towards Apple Music. Now it's up on tidal and google play, with spotify likely following it shortly. Fingers crossed The Chronic is back up too.