Upstairs Zones are Overheating (set at 71F, getting to 76F)

I have a 4 zone Carrier Infinity Greenspeed 26 Heat Pump/AC. Its the most efficient system they make. The issue i have is when the system is trying to operate for zones that are downstairs, my two upstairs zones are grossly being overheated. The short and annoying answer i got from my HVAC person is "heat rises, upstairs will always be hotter" but that answer was quickly squashed when it still happened with the doors closed. I then realized the zones were still getting air despite their dampers being fully closed (Zone Position is zero and CFM is zero). I then asked about that and was told "dampers arent air tight and air will always leak into closed zones". I feel that answer is also BS. Why have zones and pay extra to have zones if they arent going to be independent. I understand if the upstairs is a degree or two higher than downstairs but 5 degrees in unacceptable. I have all zones, 2 upstairs and 2 downstairs, set to 71F but because downstairs needs to more air to be heated, the system operates for those zones but heat comes out of the vents in the two upstairs zones which causes the temp to rise to 76F which is way to hot when trying to sleep. He also said my issue is because my house is very well insulated (hardie siding, zip sheathing, 1” rigid foam, and 2x6 rockwool, triple pane Pella windows) so a “normal” house would be colder and the small amount of air coming into those zones wouldn’t be enough to raise the temperature.

1. Zones are there for a reason, to allow for different temps in different areas. If i was a cold sleeper (tstat set below 68) i'd be hating life right now.
2. I shouldn’t have a problem because my house was built better than the norm.

Should i have him replace the dampers with airtight ones?
Also, why wouldnt they be airtight to begin with?

I know how to access the Service settings so feel free to ask questions on how the system is set up.

source https://hvac-talk.com/vbb/showthread.php?2226577-Upstairs-Zones-are-Overheating-(set-at-71F-getting-to-76F)&goto=newpost