They’ve done this previously with books, music, and other media purchased through them and they aren’t alone. Apple and Google have also been on the hook for this. This usually happens when they lose the right to sell some form of media (they make deals with record labels, artists, movie companies, publishers etc to license the right to sell that media for the purpose of streaming). You’re buying the right to stream/enjoy that media indefinitely (until they lose the rights to sell it to you and then they have to remove it from their library of streamable media). You can absolutely download that media and keep it somewhere not connected to the internet. But they can absolutely remove it.

The one exception used to be Google Play Music. Their terms were such that you actually owned the music you purchased. I assume that’s part of the reason they sunsetted that app and their music selling altogether. The cost was too high vs the number of paid users.

Apple has also done this and it was a big deal because they didn’t notify customers at all at the time.

Edit: I’m gonna add that this licensing agreement is similar to the one made when we bought physical media from retail stores. They have the right to sell it until their licensing agreement runs out. When or if it runs out they send back their remaining inventory and proof that they sold everything else. And the only reason a company isn’t requesting that media back in this event is because it’s cost prohibitive for them.