The M&M SAUA robot in the LH reservation system is an 100% automated process, and only "pure" flights are recognized for upgrading. Any code shared booked flight will not pass the upgrade check in the first place. An ADHOC upgrade at the APT before departure is more a goodwill than a standard rule.
I had not anyhow a problem to upgrade a LH flight booked under UA number last week from ORD. It was all done via the computer and did appear to be a regular exercise and not anyhow goodwill.