, the refs would notice the differences over some amount of games doing it.
I don't think this would happen.
First, refs don't touch the football as often as you might imagine. In the course of a game, referees spot the ball and might toss the ball back to the equipment person on the sideline, or receive the ball from the equipment person. You're not making long throws where you have to grip the ball. A lot of the tosses are short underhanded throws. If there is a long incompletion and I'm back judge, I toss the ball to the equipment guy on the sideline and another equipment guy brings a new one out to the umpire (unless you're doing an 8 man crew). On a 6 or 7 or 8 man crew this means not every official is touching the ball very often. when I'm handling the football, I've got 10 other things I have to do at that very moment. I'm not thinking about the football, I'm watching my assignments on the field, watching the hand signals from the umpire and referee, and making sure that I'm on the same page with them. Did we spot the ball correctly? Are the substitutions being made correctly? Are the sidelines being observed? Are the players using their protective equipment properly? Are there any players who are playing hurt, and do I need to stop the game because some 17 year old has decided to be a tough guy (an NFL official probably has to make sure no one is celebrating in any way shape or form)? Are the down and distance marker correct? These responsibilities, among others, are divided amongst the crew, but I promise you, when I've set the ball for play I've never once thought about whether the ball was properly inflated.
Second, the officials were probably wearing gloves. It was 50 degrees and raining. I would have worn gloves because they would help me grip the ball on the rare occasions that I have to toss the ball. That would have hindered figuring out the ball was deflated.
Third, you really notice the ball is deflated when you grip it. Think about the difference between catching a short toss and setting the ball on the ground, and throwing the ball for 25 yards or running with the ball (and holding it tight so you don't fumble). Officials don't grip the ball because they aren't worried about fumbling or passing it a long ways. And when we do throw the ball, we don't rear back like a QB. At the super bowl, watch how the officials handle the ball. They don't grip it the same way.
Fourth, at every halftime my crew has checked the pressure. We've never seen a problem. So, it isn't something they'd expect.
Fifth, I suspect that officials will adjust and start gripping the ball occasionally after this, just to make sure there haven't been any surprises.
Sixth,
if they do notice, and don't say anything, its because every team does it. The 12.5-13.5 might be a rule honored in the breach. In HS football, I doubt most refs are trained enough to even check properly.