This hasn't been the case for anyone I know who has been diagnosed. For all of us it was immensely empowering:

"Oh all that stuff I've been struggling with wasn't actually my fault? With this magic pill I can get stuff done too and not feel like an imposter all the time? Heck yea!"

I can imagine what you saying applying to some childhood diagnoses. I cannot speak to anyone I know who was diagnosed in childhood thinking that way though.