I´m certainly not Victoria but keep in mind that a breakfall does not necessary mean "going full circle" but rather that you fall straight down (as opposed to a roll).
So a backwards breakfall could be both a direct fall (more like getting your feet pulled out from beneath or the classic banana-peel-slapstick) or a complete breakfall (like tobu ukemi but backwards).
What is "ushiro ukemi - backwards breakfall"?????
In our dojo, ushiro ukemi is just back roll, and near to no one is able to do a backwards breakfall (would be called ushiro otoshi). I once saw a guy in a seminar doing it, but it is certainly not required of 5th kyus. I asked one of the guys who is doing very, very brilliant tobu ukemi (forward breakfall; mae ukemi in our dojo is again only a forward roll) to teach me that one, and he replied he couldn't.