I was looking at the patch notes for 6.57 and saw that the upcoming Xbox beta client will be supporting single sign on (SSO) once you've linked a Microsoft and Square Enix account during the setup process.

The Xbox Series X|S version utilizes single sign-on (SSO) authentication. Once Square Enix accounts and Xbox (Microsoft) accounts are linked, players can skip the login process and launch the game directly.
This is a huge quality of life improvement for Xbox players as they'll never have to manually enter the password and 2FA code for their Square Enix account. This SSO is possible on both Steam and PlayStation with many other games, MMO or otherwise, supporting this feature. It would also be of benefit to Steam Deck or other handheld PC users as they'd wouldn't need to faff about with an onscreen keyboard when loading the game.