nsort sorts namespaces and pages together

When nsort sorting option is switched on, namespaces and pages on the same index level are sorted together.
I use it with msort option as well.
Original behaviour sorted namespaces first and then sorted pages were added.
Maybe new sorting option can be added for this mode.
Quick response: 
Does the item `$dir_or_file not contain a property specific for folder vs file? Or is it otherwise not cheaper to add such a property?