My understanding is that in AUTO mode the heat or AC will do whatever it wants in order to get the ambient cabin temp to the setpoint.
Turning AUTO off I find makes the temp settings only a mere estimation.
So with AUTO off, setting the dials to 75 I would not expect the air to blow out the vents at 75 degrees.
I use AUTO almost all the time, only using "Hi" to speed up defrost on a winter day.