My guess is that you are referring to the "ontogeny recapitulates phylogeny" theory:
https://en.wikipedia.org/wiki/Recapitulation_theory
Which, despite the awesome rhyming phrase, doesn't really represent reality much. But even if it did, feral stage development wouldn't be reason to believe that this applies to humans.
The better reason to believe there's a chance this applies to humans, to some degree, is that humans and fish share similar brain signaling and micro biome products; which may be true or may not be! It's a big hint of a direction to look, which is great.
But even if this doesn't apply to humans, it's valuable research because it defines what's possible in biology.