This is actually more of a view limitation rather than XPages. The XPages view control simply exposes views to the XPage.
But, yes, people have been asking for resort-within-a-category to work with views for over 10 years now.
IBM even registered a patent for an algorithm that can facilitate this (it specifically mentions Notes/Domino views, too). Hopefully they’ll come through soon.
I’ve been saying since they were released that XPages will rapidly expose views as Domino’s achilles heel.