AC and backseat

You are correct, the floorboard vents are front/back.

 

I have ceramic window tint and re-direct middle vents in the front to blow in between the front seats to the rear or use floor vents. I also sometimes toss some towels to cover the seats (I have black clazzios). My 12 year old has no complaints so far.

 

On most other cars, the vents UNDER the front seats are for HEAT only. I have never seen AC vents under front seats.

 

They’re just vents, as with any vehicle I’ve even been in, connected to blend doors that meter hot/cold air. Hot air in, hot air out, same with cold air.
Now many auto climate controls will use the floorboard vents when heating, but they’re just the same tubes hooked to automated blend doors.

Side story; I did have a 1983 VW Rabbit GTI. The two center vents were dedicated heat, and the side vents were outside air,,, no A/C. My buddy would joke about creating a small tornado mixing hot and cold air.