Font Book Oddity Which Affects Only Geneva Font - What's Up?

At this time I have installed 249 font families which together have 637
faces. The fonts are clustered into sub-folders within either
System/Library/Fonts or /Library/Fonts. Because a particular font might come
from more than one source there are some duplicates.

If I resolve the duplicates using Font Book they are all resolved with the
exception of Geneva. This resolution is applied by selecting all of the fonts
and then applying the Resolve Duplicates action within Font Book. In the case
of Geneva I have to, in Font Book, open the Geneva folder revealing the two
versions of the font, then select the two, and then apply the Resolve
Duplicates action.

So, the question is, what magical and mysterious properties does Geneva have
that none of my other fonts have?

There isn't any problem, but my curiosity is piqued!