I've heard this from multiple people who have seen him play. His biggest weakness is his size. Not sure he can hold up if he's taking big hits.

"Over the weekend, on a trip to the 50th anniversary of the Roosevelt golf course in eastern Utah, Greg Graves, a veteran high school official who is very familiar with Hillstead’s game, told me his ability to throw receivers open is elite. “He has a talent for throwing the ball where the receiver is supposed to be before the receiver breaks and that is a kind of innate vision and anticipation that many do not have. This, and his arm strength, makes him a very good QB,” said Graves."

https://www.deseret.com/sports/2024/05/06/byu-cougars-mccae-hillstead-causing-stir-in-provo-big-12/