This seems like a really important point, it doesn't seem normal for a 4 year old to come up with all this from thin air. Best case, it is from TV or books.

It seems pretty normal to me. Parents and preschool start indoctrinating kids into the Cult of Stranger Danger young. And one of the things they say, over and over again, is that if anybody tries to walk off with you (as a child) then child-you is supposed to scream very loudly "Help, help, this is not my parent!"