I actually disagree, I think Combofiend made his point about proximity guard. Footsies is like chicken, you want to be at the right spot at the right time. If you were caught blocking a whiffed move, you were caught out of the moment you were backing off, instead of remaining neutral so you can whiff punish, like you would be if you confident in you position. If you could freely walk back and block you would get both the position if it whiffed (and you aren't in guard so you can whiff punish if possible) or a block if you about getting tagged, hence get their cake and eat it too statement. Proximity guard has its place in the game in manipulating the opponents movement.
He obviously understands the issue that the proximity guard box may be too wide, that is something they can adjust and he mentions that.
Edit: to kumubou about combofiend's proximity guard statement.