I'm going to wing it RoseTree, but it could be the bones are aged, very little if any soft/skin tissue would be present (especially after 6 months or so in FL weather) From the man who found the remains he visualized a young girl. Hair would be present after a few years, maybe even jewelry or the clothing indicating age.
The remains were called skeletal remains. Bone marrow would take longer to examine, if present. Dental would be out for id'ing if the child had no dental record.
It's one of the missing but it sounds like it could be Haleigh. The other day a young girl was found out here at Apache Lake. There were hopes it was one of the children missing due to the 3 who found the remains & their descripton of a young girl. It turned out to be a 20 year old, weighed 135 or so. I'm not sure I could deteremine skeletal remains age upon sight though anymore than anyone else. I'm sure it's haunting though. My thoughts are with the finders of the missing too.
Length of time to determine depends on what labs forensic samples are sent to. Each state varies. Maybe FBI has stepped in and that's why it's taking so long & not much is released. That means something big imo.