It looks like I need a login to get the article so I haven't even read it. So I have no evidence, articles or anything, but I think there must be a difference between entertaining oneself during life's inevetiable down times and what you refer to as behavorial disengagement.

I see what gratified's child is doing is much more in lines with self-comforting and self-control (which are positive traits)rather than checking-out.