i just don't buy that. i know plenty of women who are really into stuff, and also there's the whole fact that, in general, women get the short end of the stick (whether clearing up, cooking, etc) so they have less time and energy to be trainspotterish.
plus, playing guitar at a high level is no different from playing violin at a high level.
your friends must be feminists, mark. i know of plenty of women who would be the opposite.