Ds1 was dx'ed with HFA around 9yrs ago.
At primary school it gave him access to help at school with things like social skills and motor skills. It meant that his teachers knew in advance that he might get upset about things that probably wouldn't have bothered other children.
At secondary school it means that his teachers know that his illegible handwriting isn't due to laziness or a lack of care taken, and that his difficulties with group work or PE aren't because he can't be bothered to try.
He's now almost a teenager, and I haven't yet come across a situation where the dx has been even a disadvantage, never mind harmful.
Ds2 was dx'ed with AS around 8 years ago. At the time it was thought that his issues would be relatively minor.
His dx meant that when things deteriorated fairly rapidly, he was able to access the help he needed rather than facing exclusion.
Again, I haven't yet come across a situation where the dx has been a disadvantage.
Both boys know all about their dx, and both were relieved to find out that there was a reason why they had always felt different to other children. Avoiding the dx wouldn't have done them any good.