The poster clearly meant it with a flavor of whimsy to it, not in a derogatory way. Maybe also as a tongue in cheek jab at how people they perceived as overly concerned about supervision would describe such kids.
I'll put my hand up as having been a joyfully feral kid once upon a time.
Are you in a "wild and unsupervised" state when you leave your house and go to work?
I never said the feral kids were participating in those activities. :-) Look, it was loose use of the word, you're placing way more judgement on the term than was ever intended. Yes, the children have homes and parent, of course they're not feral.