Anyway, I think that it's an actual bug with cua-mode or something because the deactivate-mark-hook isn't fired when the region is removed, repeated pressing of C-g doesn't fire it either.

It's also a consistent behavior, when cua-mode is active the deactivate-mark hook is not fired

(by using git blame) I noticed that there was a change in September last year or something which modifies some bits about how cua-mode handles the mark.

Please tell me if I'm wrong or if there is some additional digging I should do to further diagnose this issue.. 

--