A hatchet wound could go to the bone and not be fatal so long as it didn't sever an artery or the spinal cord, IMO, or at the very least, not be the thing that ultimately killed them. That they knew one boy sustained a chop wound to the head ... well, I'm pretty sure that went to the skull considering how close to the surface the skull is.
The neck has musculature and tendons beneath the skin that could have survived the fire (as they take longer to burn), or survived enough in it's burnt state to show an unnaturally clean, deep cut/slice. Also, the collar bone or underside of jaw could show chop wounds and still indicate the hatchet struck in the neck area.
I'm not sure what we're debating exactly, to be honest. Obviously, wherever they were in the house in relation to the fuel used and the hottest point of the fire, however the fire burned, whatever exploded or didn't explode, whatever accelerant was used, the facts are the ME had sufficient bodily structures and tissues to make the COD determination, and also to determine where chop wounds were inflicted. Therefore, no matter how horrific the fire was/looked, how long it burned with the bodies within the house, the heat level wasn't 'crematorium' heat level. If it had been, in 30-45 minutes, the boys would have been completely incinerated. Since they were not incinerated, the heat level had to have been such that some tissues (tendons, musculature) survived/were present, even in a burnt state, and still told a clear story. :twocents: