wasatch_ratPretty much the only people that bother differentiating between wackflip japans and flat 3s are people that can't do either. You're not wrong, but at a certain point its just not worth splitting hairs. You don't hear people calling dub 10s d spin 7 to lincoln.
just did a quick googlage of flat 3 and theres some inconsistencies.
and second vid
I would consider the first video to not be a flat 3, more of a Lincoln with a 90 in there. While the 2nd vid is a pretty decent example of what i would consider a flat 3.
Not trying to be a dick, and not particularly trying to be nitpicky, but they are 2 very different tricks, with the flat being immensely more flowy, and harder to accomplish.