So, they have a hypothesis.
I personally doubt the effectiveness of surgical and cloth masks because, despite my best efforts, my glasses fog up when I wear them. Obviously, some of my breath is bypassing the filter.
Unfortunately, the people making national policy couldn't fog a mirror, w/o a mask.
Look up Brownian motion.
Maybe you will understand after you read it
It’s physics.
Of course, if you have a gap then Covid can side step.
Again, you are trying to reduce the viral load...not totally eradicate it. No one is going to walk around in a biohazard suit to the grocery store...well a few have but probably as some stunt.