Ah yeah, that page has the statement I vaguely remembered in my head but thought was in the community somewhere:
"The declared intention of the user type. This can be set, but does not change any Canvas functionality with respect to their access. A user can still be a teacher, admin, student, etc. in any particular context without regard to this setting. This can be used for administrative purposes for integrations to be able to more easily identify why the user was created."
So I that somewhat confirms that it's more of just a back-end info field available via API than anything else.
-Chris