Ask yourself this question. Why did Bryce Young throw the ball in the endzone with his head pointing down and his feet sideways?
My answer is to avoid a safety. If so then it was intentional grounding. But you say there was a receiver in the area ok maybe there was but the ref should still throw the flag and clean it up on replay. You see now you can use replay to get the play call correct. With no flag thrown you can't use replay to call grounding. 105,000 people saw intentional grounding on the play and two refs didn't. But then 1 official saw targeting and threw the flag when the player called for targeting didn't get within 3 feet of the head and neck area of the ball carrier. But for safety sake the ref throws the flag and cleans it up on review. Then during review the neither the replay official nor the ref looked for Young being down. Which is something that can be cleaned up during review. It happens all the time.
It reminds me of a play that happened to me during a state playoff baseball game fortunately I made the right decision on the fly. Bases were loaded the batter hits a hard line drive down the left field line. Just before the ball hit the ground the 3rd baseman steps between me and the ball. I was clueless as to fair or foul. I immediately point to the inside indicating fair, three runs score on a stand up double. The defensive team went apeshit in the 3rd base dugout and the coach was livid. I met with my partners and explained I was blocked on the play. One of my partners was sure the ball was foul. So I changed the call to foul and put runners back on base and the batter in the box with a strike. If I had originally called the ball foul I couldn't have changed my call because I had no way of knowing where runners would have reached. Once a foul ball is called it is always foul and can't be changed but by allowing the play to continue and not killing it I had a way to get it right. This was before there was any video replay so I had to depend on partners to help correct the issue. I called both coaches to the plate and explained the situation to them and why I made the original call of fair. The batting teams coach was still not happy but seemed to understand. After the game the upset coach caught me leaving the field and admitted that I had handled the situation about as well as I could have under the circumstances and was appreciated the fact that I was willing to change my call to get the play corrected. I knew all along some team was going to be upset which ever way I went.