As for registering with a phone number, this is an additional loss of privacy if you intend to use the exchange without KYC. Please note that if you register using a phone number, this number will now be embedded in all important functions when working with the exchange, any device change, security settings, withdrawal of funds will require SMS from you everywhere.
This is one mistake I have made in the past that has affected me strongly as an early trader in the crypto space. And I have learned from it. Back then, before I actually learned how to reduce risk and identity protection, I saw the mobile number form of registration as the easiest, not until one of the exchanges stopped sending codes to my country number. No reason was given for that; some times it was actually from the network provider, but you never could tell when it was from the network or from the exchange itself. Another challenge for the mobile number registration option is that when you travel outside your country to neighboring countries, your SIM stops receiving service, which will be a greater problem.
Such options should even be completely removed from registration means; they can be added as security measures that one can either choose to use or avoid.