In some ways you could argue Andy took a while to reach his potential, but he was moving in the right direction all the time, because he was focused, not to mention brilliant.
I think Mr M was a slightly different case. As we saw in the documentary he is still very much a man shaped by the trauma of his childhood. I still think people don't truly take on board just how much that event impacted on his growing years. Not just being in the school at the time, but the aftermath of growing up in a town where the surviving children had to cope with the guilt of the survivors, and the grief of the adults around them. You wonder just how much the surviving children must have subconsciously felt all of the time that they shouldn't be naughty, that they needed to be grateful they were still alive.
Add to that the pressure he has lived with from the Great British Public, since they first became truly aware of him when he was about 18. The fact that unless he won Wimbledon he would be deemed a failure - another in the long line of British tennis players who always fell short.
That to me is why I see his achievements as being so great. If you look at the context in which he has become a multiple GS winner and Olympic champion, personally I think he is on parr with any of the others. Could Federer, Djokovic, or Nadal have achieved anything like what they have achieved if they had been expected to do it under the conditions Mr M has had to? I think John Mac and Boris Becker have said the same.
To my mind the issue is not that Mr M took a long time to reach his potential, it's that he managed to do it all. That's the incredible thing.
Mind you the fact that he is also brilliant has helped....!!!