Interesting post Sunshineray, and just sets up several lines of thinking for me that don't lead to any conclusive speculations, just more questions.
I have no idea if the information you are referencing is accurate, but for the purpose of this post, we'll assume the GH source is correct. The only thought that comes to mind is that this Perp had himself so well covered/sealed that he didn't leave much DNA as stated in your above post. That's really quite remarkable, if true.
To *not* leave DNA, he would have had to have worn some sort of "clean room" suit that you see in labs or highly dust sensitive assembly lines. He might have even gone so far as to shave his body. As to the hair....well that doesn't add up, unless he had it under a clean room cap. (They look like shower caps). With what we believe must have been a violent struggle, you would think a hair or two (or several) would have transferred, and skin cells; particularly under the girls nails.
The lack of DNA also suggests there was not a sexual assault, (which doesn't align with my Perp profile), or that he wore a condom, or removed the evidence with bleach, etc.
If the GH source is accurate, (unconfirmed), the lack of DNA (except the touch DNA) adds a whole new dimension to this. I sincerely hope the crime scene was handled properly and wasn't contaminated.
Amateur opinion and speculation