The bug is that there has been an unknown BDB limit the in 0.7 and earlier code for quite some time.
Not being aware of a certain property/feature of BDB does not make that feature a bug.
It makes the code you write using it a bug if it relies on it not having that property/feature!
Well I find it a bit odd that no one ever knew about this limit before. How can that be when we've always had people saying we need a larger block limit? How can that be when anyone can look at the blockchain and see there is a limit, and that anything past that limit gets rejected? Maybe I'm not understanding the problem correctly but this baffles me... how could the limit be unknown.