Was the proposed swimming caps for black hair rejected by the International Swimming Federation because it provides some unfair performance?

I read on https://www.theguardian.com/sport/2021/jul/02/swimming-caps-for-natural-black-hair-ruled-out-of-olympic-games-alice-dearing (mirror):

International Swimming Federation rejects use of Soul Cap, saying it does not ‘fit the natural form of the head’. Swimming caps designed for natural black hair created by a black-owned brand will not be allowed at the Olympics.

Was the proposed swimming caps designed by Soul Cap for natural black hair rejected by the International Swimming Federation on the grounds that it provides some unfair performance, or simply because of how it looks like? If the latter, why would the International Swimming Federation care about how a swimming cap looks like?