One of my nostrils is almost always partially restricted. Yes, I have airflow through both of them, but it's almost never equal. Right now easy breathing through the left with some resistance in the right. It slowly shifts back and forth throughout the day.

It's very obvious when I have a cold. I often have one fully-plugged nostril and one not, which also shifts back and forth seemingly randomly.

I think what I'm describing is actually the norm but I haven't exactly surveyed the population.