In GEOD, the author alternates freely between "the Duncan Idahos", "the Idahos" and (gasp) "the Duncans". I don't recall ever reading "the Duncans Idaho", but it would be cool.
I think that, even if you accept Apple's rather awkward usage, it's less clear that it works for the Duncan Idaho case; that's a single name which happens to be split into two words, whereas the 'Air' in MacBook Air is a descriptor.
