But I think you could argue that not all API are alike.
On the one hand you have APIs like, say GTK+ or Qt, which are rigidly defined and guaranteed to not break between versions.
Then you have stuff like the Linux kernel where you of course have an API, but it is not guaranteed to be stable between even minor version numbers.
GNOME-shell extensions fall in the latter category.
I have shown you a link to a blog post from a Gnome developer describing that what he calls "the extension API" and where he decribes that they will break it if they want to. No superpowers needed, I have backed up my claims, time for you to do the same.
I am not sure why the lack of a stable API is anything to be upset about though. The kernel has the same policy, and everyone seems to agree that this is a good thing.
I think the same reasoning is applicable in this case.