Interesting. I leave the floor and face level vents open all the time and I've never had dry eyeballs. The only time I don't is before the car warms up, and then for a minute or two I send all the air to my feet.
But even set at 73 the air was 110.
It's required because I'm curious.
My friend with a Cadillac warned me that I should get a non-automatic heater, but with used cars, one doesn't have much choice.