I think you're retroactively altering your memory. Even when Mayor was a sophomore, I personally wasn't sold on him as an NBA player (thought he was a 2nd rounder, and those selections can be toss-ups). I don't understand how you think he Mayor was always NBA ready. He worked hard at his game to get to where he is. His bball IQ is great, but his raw talent does not jump off the screen.
I remember going to a summer practice with some of the guys from this board. Everyone was talking about how Dre may be ready to make the leap to an NBA guy as he was heading into his junior year. Lots of hype over him and Josh. Some over Spencer, but it was muted. Then at the practice we all saw Spencer whoop everyone's ass and pull off one of the most gorgeous moves I've ever seen on the baseline. That's when I personally knew he was NBA bound.