Did the PA coroner have her first, or was it the WV coroner? My assumption is that the PA coroner did the first tests (as her remains were found there), then the remains were sent to the FBI and more information about the confessions and charges against SE were released. As it now looks like SE is going to be prosecuted in PA, my guess is that the PA coroner wants to make sure all the bases have been covered before SE is transferred to adult status, the trial gets underway, and Skylar's remains are returned to her family permanently. This is the PA coroner's last chance to tie up loose ends and to confirm findings before Skylar is laid to rest forever, so I'm sure they're just being thorough to ensure the air-tight conviction of SE. JMHO
Thanks, being in the UK I'm not always clear about procedures in the US.