My Opinion Only and I say this without a thorough theory, (yet) She wasn't found "in soil", she was on a concrete slab. I don't recall the exact temperatures there during the month she was unaccounted for, but, being frozen and then warmed up can deteriorate bone fast. If you recall HG was found in woody damp area and I'm sure the insects are going to be different and different rates than where AJ was found. I am skeptical about a pesticide or some other chemical that could have been poured on her to accelerate decomp and ruin (potentially) DNA.
Didn't that neighbor out on Smith's Ferry say it was only in the past week (prior to 4/9/2015) that he had seen the vultures?
It just seems to me that IF this was a simple GS wound the ME would have DX it at that without further info from and Anthropologist.
It is my belief there is something there that has LE and the ME stumped.