[est31]

Indeed I was. E.g. check this figure: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5053491/figure/...

One nostril has basically no pressure changes while the other one does. How can you smell that way in stereo?

[jessaustin]

Presumably breathing has no effect on the diffusion of odors from far away to the immediate vicinity of the nostrils. So, diffusion can also take odors from the temporarily-inactive nostril deeper into the sinus.