Does heat come out when you have the max ac on in a 1998 ford expedition?

My mom has been having problems with her heater in her 1998 ford expedition. She took.it in and they say it works if you turn it to heat then turn the other one on max ac? That's how they say the heater works? How could it be hot if its coming from the max ac? But it was cold coming from the heater/panel/floor or just panel or just floor. There trying to say that's how its supposed to be but it would have to use freon if its on max ac? There wanting us to pay them for working on the vehicle but still have no heat but he says it works on max ac? We need to know if that's true and how the heat works througH the vehicle

Get a new car

The heat has nothing to do with MAX A.C.
Just put it on panel/floor or floor only, etc, then turn the blue/red temperature knob up.
If that doesn't give you heat after five minutes of driving, it's broke.

Temperature is not affected by choosing Maximum Air Conditioning)
temperature is affected by the knob that goes blue to red opening a door to expose the heater core in the HVAC assembly to maximum "air conditioning"( which does not mean hot or cold, just air being conditioned ya know)

Picture of a very similar(same) ford ranger HVAC system
Notice the blend door actuator(temperature door) usually vacuum operated on fords, I have had to fiddle with some, either line leaks or unit replacements