Well an umpire wouldn't think in those clinical terms but they'd think that a ball trimming the bails is not out vs a 1/4 of a ball hitting the stumps is out.In the eyes of the system it is the same though. There's absolutely no way the umpire thought "ah I think that's hitting one inch above the bails vs one inch below, I'll give that not out" so the marginal difference on the projection is immaterial, because the projection only really serves to put things in one of three boxes labelled "out", "not out" and "umpire's call". I happen to think he's probably correct that ultra-marginal umpire's call decisions should be not out but the "line" for umpire's call should be moved to the top of the bails, so the one just now would have been three reds anyway.
The idea that last decision is a bad one because the Broad decision was given not out is just silly.