well. we hit a huge play last week on it.. which I found strange.
maybe the idea is that for players keying on the QB.. focussing on him.. they never really see the RB.. so it doesn't matter if one is there or not
there are lots of "keys" for defenses... based on position and down and distance.. does the OG opposite you pull.. does the OL fire out or stand up.. which way does the RB break.. this is especially true in option defenses with very specific assignments.. QB, pitch man, dive back.. and the offense keys as well.. does the LB or DB play man or zone.. does he turn upfield or outside.. if showing blitz, does he blitz.. is it really only 6 in the box or are others cheating in.. etc.
I think this is why GS has CBs only focus on the man they are covering.. they go where he goes and read him.. they never take a peek at the QB and can never be clued or fooled by anything he does.