Mendoza was a Top 25 prospect overall in the Portal. He had a 93 rating (same as Xavier Lucas, for comparison). His recruitment was streamlined, as it is for many Portal QBs, but he signed a two-comma contract.
I bring that up to show how the national perception (as reflected by his rating) outpaced the board opinion. I expect a similar thing to happen if Bailey enters the Portal. In his last game, the announcers were talking about him as a future Heisman contender. Doesn't mean it's true, but it reflects the gap between the national perception and the perception on here.
As for the substance of your post, you cited Bailey's QBR against us. He actually finished 14th in QBR in the entire country. Remember, he's only 19. He's 6'6, has a strong arm, can run, has great character, and is clean medically. He has 21 starts as an ACC quarterback with two years of eligibility left. There is a lot to like.
I believe he played poorly against Miami because (1) young quarterbacks have bad games; and (2) his supporting cast was overwhelmed. If you put him behind an elite pass protecting OL, I expect him to thrive. His trajectory has been straight up since high school. He keeps getting physically stronger and his mechanics have improved every year. And he's already a good ACC QB, so the floor is high.
The truth is I don't know what Miami wants to do. Bailey might not even enter the Portal. But if he does, expect to read a lot of nice things from people who live North of Palm Beach.