So to the rules of the game it's holding. But, and there is always a but - here is the issue from my perspective.
First and most importantly - that flag is thrown on plays like this (which let's be honest happen on almost every damn pass play of every game played in the NFL) maybe 50% of the time at best. It's the definition of the often used "ticky-tack" penalty.
Yesterday the officiating crew did a pretty good job I felt of keeping these calls to a bare minimum and this is the key point. The players 100% adjust throughout the game based on how the officials call the game. We all do at all levels of sports that are officiated. If you have played a full game where after a quarter you know they are being super strict on stuff like that then you know it's something you just can't do - that wasn't the case yesterday.
I just don't understand how, after officiating the game for 58 1/2 minutes one way, you decide to get ever so slightly stricter on that one play. That's simply poor officiating and the worst part is that prior to the play even happening, those officials know the implication of throwing a flag and what it means - basically game over and a season decided because of it.
You look at the AFC title game where that dude from Cinci makes that bone-headed play on Mahomes at the end. That's an example of something you can't let go. That hold? Come on now.
So to wrap it up, you have a ticky tack penalty that is really a coin flip call at best. A call you haven't been making all game that you know in that situation has HUGE implications. I'm sorry but the default there has to be no flag unless it's something so obviously egregious which that wasn't. You clearly can't mug the receiver on that play but that was the contact that was crucial factor in deciding an entire season of the National Football League? Nope.