If you had a bunch of human children together and provided them sustenance and all that without adult interaction they might still develop normally and form their own language and means of communication with each other.
We don’t know for sure because such an experiment would be horrible and extremely immoral. However I do remember reading a while back that a similar situation happened where a bunch of deaf children in a an environment without much adult interaction did manage to create their own sign language to communicate with each other.
So it seems the feral child phenomena might be due to the fact that the child is alone rather than simply due to the child not having adult interaction.