Different finish sheens? Or different stain colors? Photos would be very helpful.

Different stain color. Work has not started thus photos not available.

I would not choose to have my floor that way.

A single flooring choice (colour/species) throughout a home indicates high-end home/finishing. The more you 'break up' the flooring into different elements the "lower" your overall look becomes. The exceptions: kitchens and baths. Gone are the days of "theme" flooring for different areas in different colours.

If you are going to have two different colours of wood flooring, at least make them very close in tone...one being lighter than the other. But a new build has no need for two or more different floors (except for kitchens and baths...these are still acceptable to have different choices).

Absolutely. But how do they meet at the stairs?