My statement is based off of performances from McNeal under similar situations. For an example, see the UT/A&M game from '04. Once Texas unleashed their defense on him in the 2nd half (one series McNeal was sacked on 3 consecutive plays), he was completely ineffective.
If you watched the Rose Bowl, most of the time Vince was making plays, he was under a lot of pressure. There's a pretty big myth about Texas having a great OL. The truth is, they're a great run blocking OL. But they are just above average in pass blocking.
It's not always about Vince "making runs". He's able to buy himself time by making people miss even when he's still in the pocket. He's completed passes with people hanging on him (see the Roy Williams clip that is posted on this board for proof). Those are plays that Reggie doesn't make. That is a statement I can make because there is physical proof that shows it.
Now if you put Reggie behind a good passing OL and he's on, he will pick you apart. But there are a lot of QBs that can do that. How many can do what Young does?