It's soft KYC in the form of a phone number in order to identify users. The custodial part of the app needs a way of identifying users and phone number is a simple one.

The non-custodial side won't need that, and we're aware that sim swapping is a thing so we'll probably be requiring 2FA or some additional layer of security above certain threshold.

Because it's a shit product, from soneone who doesn't understand bitcoin.