Theres a few different types of autistic people here.

So, I think its like this : one of the biggest differences between an autistic who goes undiagnosed or untreated , to a person who is treated . A person like me who goes undiagnosed will master all the techniques that hide their problem , like eye contact ... Possibly better than a person who is diagnosed early. But they will not learn all the self care skills and strategies that help mitigate harmful effects and improve functionality as a civil unit ... which the diagnosed individual will likely pick up. Its not necessarily from those skills being taught just knowing what the issues are helps you develop those skills. Similarly , it can be much easier to learn to hide a problem when you don't know you have one in the first place ...