Z32 operation of AC correct ?

1991 tt z32.
With the car running, and the air con./heater temp. Set to 40, then auto button pressed on, the ac compressor kicks on. Is this normal operation? Press the econ. Button and compressor turns off.
Seems strange to have the compressor turn on for heating.
It blows hot air. No issues there.

 

I have a 91 tt. The a/c and heater operates as you described. Doesn't make sense to me either.

 

Heating and cooling at same time is for drying out air: stops the windows from fogging up.