It's not necessary, it's just another angle.
Adding extra people to what we know to be true doesn't seem to clarify the facts, but rather confuses them by introducing elements that are not supported by any facts. Maybe the perp or perps that abducted the children were aided by two teenage boys, or two teenage girls, or two moms pushing strollers, or people watering their lawns or ... the list goes on forever ... but there's nothing to suggest that anything except a perp or two were involved. What is it about teenage boys or girls or transients that makes it seem reasonable to add them to the facts?