Ha--one of the problems with changing an ending *y* to *ies* for names is demonstrated with the name *Mary*, whose plural would in that case be identical to the plural for *Marie*. Mr. (or Ms.) "quite incorrect" is amazingly assertive for one so ill-informed.

As it happens, I live in the Rockies, and was aware of the exception. But I presume that Mr Balboa and others with his given name are Rockys.