Do you know if those characteristics are also true of younger offenders? They wouldn't have as much flexibility to leave town or even miss school, for instance.
I'm not sure if really young offenders have been studied that much. The, sort of, definitive study of child abduction murders, the Keppel & Brown study, contained between 750-850 individual murder cases and there were offenders as young as 16 in that study but I think there was only one. Just going by memory though. Not saying they are as rare as that in reality, just what was studied.
We once had a verified member of LE posting on these threads who had some very valuable info to share on these types of offenders. This poster said that it is common for this type of offender to be a sort of "social marginal," with a history of changing residences frequently because family often shifted them around. Like, there is suspicion of child molesting in one town so he goes to live with grandparents for awhile.