They say kids with Aspergers are typically about 2/3 their age in social development. That might be what they mean.
If so, I think that's a bit misleading, because autism is more about the brain developing differently than more slowly. "Delay" suggests people can catch up to "normal", but that's not exactly what happens, it's more about learning to compensate for the differences, I think.
Sounds like the usual kind of misunderstanding.