Appropriateness of prospective PhD supervisor reviewing scholarship application before submission
It is totally normal that somebody helps with applications.

This is true, for example, for applications for scholarships (where potential supervisors help) but also for applications for grants (where, e.g., many universities have specialized units to help applicants to formulate their proposals).

Regarding fairness: I do not think that this is the right question. Unless the rules for the scholarship do not state otherwise, you can use any help to prepare your application you can get (of course, cheating is not allowed - e.g. accepting help for an online language assessment by a native speaker would not be okay).