For some reason I assumed that you have some interest in it being a "proper" backflip, when I read the word backflip I thought of the trick itself along with all of the player-made conventions and standards there are in tricking.
Most flips hasn't had dubious situations as far as I remember because it's always a high jump and mostly about the set up, not so much the technique of the flip itself, so everyone ends up doing it similarly. When I questioned what a backflip is I was imagining potential submissions similar to the attached replay or more extreme.

However if you mean a backflip in the most reductive way possible, then I think I'm not opposed to the idea. Running records have been removed in the past in part because it's difficult to quantify, and to some extent I feel the same about a backflip, but not nearly as much. Fine by me as long as other lmods agree.

On the basis of it being such a simple trick, I think this should really be the only speed trick record, otherwise we'd be hard pressed to argue against the same record for other tricks.