It sounds like you're asking two separate questions.
It's certainly sounds possible that one can meet the criteria from both ASD and SPD.
It might also be true that under current guidelines both can't be diagnosed in the same individual.
That said, having ASD without adequate support might explain why one has developed those traits and that might be considered a reason to dismiss SPD diagnoses in patients with ASD.
I have no further insight into that matter but I know within my lifetime I was first diagnosed with ADD. At the time ADD wasn't allowed to be diagnosed with austism or with Asperger's. Fifteen years later or so I was diagnosed with ASD, the terms ADD and Asperger's no longer appeared in the DSM and ASD and ADHD were now allowed to both be diagnosed in an individual.
Sometimes the experts realize one can have two things they didn't previously believe could exist comorbid so even if the current diagnostic criteria says they can't, it might just be a matter of time until the understanding changes.
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"If you stick a knife in my back 9 inches and pull it out 6 inches, there's no progress. If you pull it all the way out, that's not progress. The progress is healing the wound that the blow made... and they won't even admit the knife is there." Malcolm X
戦争ではなく戦争と戦う