That's not right. Tua played well all year long. He was 49 for 77 with 11 touchdowns and only 2 interceptions. A td every 7 attempted passes is pretty darn good. His rating for the year was 175 according to this site https://www.sports-reference.com/cfb/players/tua-tagovailoa-1.html
You can say that he didn't know how Tagovailoa would play being put in such a tenuous spot in such a big game, but he knew Tagovailoa was a good qb.
And none of those plays or snaps against a defense worth a spit. Georgia was his first test. He passed. But no one knew what Tua was going to be able to accomplish in that game until he got the chance.