We currently require verification on each partner site to ensure that the person signing-in is actually the holder of the email/phone. In the future though, we plan to allow a user that's authenticated at one Rownd partner to click a single button on a second partner site to simply pass the existing verification and account info across. In that case, no email/sms is needed as long as its done in the same browser/device.
Thanks for the question and your support!