Now if a team of say 7 developers were working on this, and they spend a small amount of their time doing formal bugfixes, then it would make sense.
Often things get fixed that doesn't appear in the release notes, so I suspect that like any reasonable developer, they fix a bug when they come across it.
Working on a large project myself, you really just need one idiot that is not rooted out by the management (because they either talk too well, play the toady, or whatever), to introduce hundreds of really difficult to find bugs. It works best if this person knows they mess up, and go on the attack whenever it seems that an issue of theirs is uncovered. Management that doesn't actually code, see this guy always berating people about bad code, so they often think this person has the highest standards (when it is the opposite, really).
Ok, I should stop this before it turns into a proper tirade... :-P