@StanislavGrinkov seems this is definitely a limitation on the GitLab side as reported at https://gitlab.com/gitlab-org/gitlab/-/issues/335143. I've updated [1] to reflect this. Please note we're planning to move new / existing account requests away from GitLab into a separate tool we'll be building.
Thanks for reporting!
[1] https://wiki.gnome.org/Infrastructure/NewAccounts#preview