I don't think either "yes" or "no" would be an appropriate answer for this question. Depending upon circumstances, either may be correct. It doesn't seem like autism is the sole determining factor when explaining a person's overall level of intelligence.
If ret*d means "slow", then in certain situations(like when socializing), a person with an autistic brain will be likely to react more slowly and not necessarily appropriately compared to a person with a neurotypical brain. Yes, autistic people would probably be relatively ret*d in those situations.
But the same person who had great difficulty in those situations might react more quickly and much more appropriately than a person with a neurotypical brain would in certain other systems, like when trying to understand a system. In those situations, relative to an autistic person, a neurotypical person could be considered ret*d, but the neurotypical neurotype is the predominate neurotype and so said neurotypical person's reactions would be considered "average" and not "ret*d".
And "neurotypical people" and "autistic people" are not respective homogenous populations. There is diversity in intelligence between individual members of each of the two respective populations. At a particular task, an autistic person may be considered "ret*d" and another may be considered "average" or even "above average", in the same way that a neurotypical person may be considered "ret*d" in one situation, while another may be "average" or "above average".