Absolutely we wont know for sure for a few years. I agree with that.
White was actually 4th in the nation in passing last year. Still very good, but just for the sake of accuracy ...
Even so, it's fair to point out that big college passing stats aren't very reliable in determining who will be a quality NFL QB. If you go down the all time single season NCAA passing leaders list, it takes getting to #39 on that list (Matt Ryan) to find a QB who had a strong NFL career. In fairness, Derek Carr is #9 on the list, and he at least has the start of what could be a strong career, and there are 2-3 others that are somewhat higher than Ryan on the list and may end up with very good careers, but the highest of those is #18 (Mason Rudolph). It's really surprising how few of the top 100 college passing seasons were by QBs that ended up having strong NFL careers.