I was just talking about the apparent problem of not having a stable theme API.
The developers never promised to provide a stable theme API, even selecting themes as a user is basically only possible via "gnome-tweak-tool", so this had "alpha code" written all over it from the beginning.
E.g., the attitude of the dev in response to reasonable argument from his users in https://bugzilla.redhat.com/show_bug.cgi?id=485846 is pretty much "I'm not changing it, just because". That would make me rant and foam at the mouth because a reasoned approach patently failed in this case.
Even this case isn't as clear-cut as you make it out to be, especially if you look at comment #14.