Exactly. Reinfections from other viruses are not unheard of. One case really says nothing about how likely this is to occur in other patients.

Therapies with monoclonal antibodies might handle this case, in particular, cocktails of antibodies (like Regeneron, Vir, and Sorrento are making) to reduce the risk of selecting resistant mutants (if you target multiple parts of the virus proteins, they'd have to mutate all together to gain resistance, which is a less likely event).