Good point. I am in the same boat as you, with the comorbidities. I was diagnosed with CPTSD before I realized that autism is part of my profile. The way I experience my autism, I suspect, exascerbates the dissociative delayed emotional response.
I agree with you though, the survival response is certainly a big part. Now that I'm well into my recovery for CPTSD, I feel like I can separate out what's more autism related and I can tell that it certainly plays a part, a big part in the delay thing.
It's actually helped me, in some ways, when I compare myself with some people with CPTSD, I find that my extra autistm-accentuated-ability to shut down or delay my emotional response has allowed me to survive and carry on with incredible endurance and acheive remarkable things, that perhaps I wouldn't have, had I just had the complex trauma -CPTSD, without the autism.
On the other hand, the markedly extreme delayed response thing, has meant that, when It all caught up with me, I became so socially withdrawn and avoidant that I can no longer work or study outside the home, as the trauma symptoms mean that my life revolves around therapy and fulfilling family expectations, with more time needed for complete social withdrawal.
So the two comorbities, I find, have positive and negative co-reactions and consequences, comparatively speaking.