Heater Control Inside, Air, Outside and Defroster Positions

[Rich72C10]

So, cool weather is upon us - YAY! So time to release the hot water, I have a manual water cut off valve to insure no hot water gets past that lovely vacuum control valve to the heater core for summer time :-)

But I have a question about how the top control lever works on a 4-season's system. When I go to Heater (middle row) and then Hot (bottom row) the Inside, Air, Outside and Defroster selector (top row) bounces to Air/Outside. If I try to take the lever to the Inside position, the middle/bottom bounce back closer to cold/AC (though not all the way).

So, when in Heater/Hot mode is putting the top row to "Inside" an invalid position?

Otherwise everything on my 4-seasons works. All the doors open/close when the levers are moved to their various positions. My control is a 2-port vacuum controller (not sure why some trucks have 3-port vacuum).