I don’t know if that is gonna work for him. Per the op’s original post:
Will he be able to “Add a New Domain or Subdomain” from the panel without a hosting plan?
As I don’t have a “registration only” account, I don’t really know what facilities are available to him for redirecting the domain, but I know that he can’t edit DNS records. Hopefully, someone here that has such an account can point him in the right direction.