I went biking the other day up some steep climbs. I've got the covid-19lbs...so I was a bit winded. Plus it was surprisingly hot that day. Nonetheless, the neck gator absolutely had an impact on me. And as
@dad4, rightfully pointed out elsewhere, if the air is blocked by the mask, it will just find its way out around the nose or somewhere else.
Don't get me wrong, I believe in masks when it comes to indoor activities or areas where you can't socially distance and are standing next to people for an extended period of time. There is science there.