Bill Belichick doesn't care about your rules, written or unwritten. Is it completely bad form to try a ludicrous fake play when you're up by 22 points with five minutes left? Yes, and Belichick does not care at all.
This kind of fake is impressive in its audacity. It's not so much a football fake as a line shift in hockey. It's weird to see the Patriots burn this at a meaningless point in the season, but Belichick has never let future concern get in the way of trying to make an opponent look foolish.
Also watch the ref. He's scurrying around like there's no tomorrow. Solid backpedal too.