Some language teams, like Polish, already show “Different user?”, and personally speaking I think that it makes so much more sense. “Not listed?” doesn’t really convey anything and can be pretty confusing to users that do not know what that button does. By renaming it, it makes it more “straight-forward” about its function.
Originally reported here GDM: Rename "Not listed?" to "Different user?" (#8583) · Issues · GNOME / gnome-shell · GitLab, but I really feel like Discourse is better suited for such design discussions.