I think my sister is a good example of why autism can be different from ADD in very fundamental ways. I have no doubt that she has some form of ADD, and my mother believes it also. But my sister has also spent her life as a social master. She reads people very well. She has always been popular. She talked her way into a lifeguard job when she wasn't old enough and hadn't yet completed the training. She won the most coveted awards in Middle School and high school. She makes a huge amount of money in her career, which is public relations.
Yes, her mind has trouble staying on task and she constantly seems frazzled. But her social gifts have always won her a pass on it.
And you couldn't find someone who presents more opposite from classic autism if you tried.
I do see the similarities with my AS son, and as with so many things there is some sort of relationship, but it's the social thing that distinguishes. While those on the spectrum may be social, they are never socially TALENTED, and it is that fundamental barrier that marks their lives. But someone who is ADD CAN be socially talented.
Why would it matter? Because the labels create the protocol. The protocols that help my son are not the protocols that would help my sister, and vice a versa. If she had been labeled ASD, her entire life would have been derailed for all the wrong reasons.
I have an AS child that pretty clearly does NOT have ADD. Certainly, he can space out. But the CAUSE is different than with ADD. If he has trouble staying on task, it's could be because he is overstimulated, or tired, or bored, or stressed, or just in need of a break. Most of the time he focuses brilliantly.
_________________
Mom to an amazing young adult AS son, plus an also amazing non-AS daughter. Most likely part of the "Broader Autism Phenotype" (some traits).