Ah. I was going to the song in Liked Songs, then tapping (...) and View Album. That does not have the control you're talking about. I thought this would be the same menu as if I saved the album, then accessed it through the Albums tab of My Library. It's not. I see the option you're talking about when I do that.
If I forgot to do that, then I have to save the album on one album menu, navigate back over to the Albums tab, then like all songs and unlike them, then unsave and remove the album. This is still somewhat tedious, but not as bad as unliking every song individually.
So I guess the bug is that there are multiple versions of the View Album menu, depending on where you try to access it.
I also think it's a basic UX principle, that if I use a binary switch control to do something, turning off the switch should reverse the effect of turning it on.