[bozlax]

You're not HU until the end of the flop. If you're behind, you don't have enough outs to get ahead. You're WAY more likely to be ahead than behind.

As has been said, WA/WB is overused in this forum, almost to mean, generically, that we are either ahead or behind. This simple fact is true so often that we don't need a name for it, or, more precisely, we call it "poker". Moreover, one might play a line that is identical to a WA/WB line for some reason other than being WA/WB.

Hero needs much more evidence of being behind before he should slow down, here.