My point exactly, he didn't throw it away, he didn't save yardage, he didn't stop the clock, he didn't get another down.
You might be thinking too much about the words "intentional grounding" rather than the definition.
8-2-1: "It is a foul for intentional grounding if a passer, facing an imminent loss of yardage because of pressure from the defense, throws a forward pass without a realistic chance of completion. A realistic chance of completion is defined as a pass that lands in the direction and the vicinity of an originally eligible receiver."
He was facing an imminent loss of yardage, he threw a forward pass, and there were no receivers in the vicinity. It's IG.
E: I guess depending on how you read the word "lands" maybe it's not. I feel like this has been discussed before as some theoretical that you'd probably never see. Maybe I'm wrong though!