Things Every Homeowner Knows About Hiring HVAC Companies: Heating data simulation analysis

I wrote some software that will look at the historical hourly average temperature over various years and simulate energy consumption for heating. It uses the 'detailed heating data' sections from the manufacturer spec sheets for various models for the btu output and kwh consumption. Most everything on the list is a 2 stage pump, but I just simulate them as if they're only ever running in the high stage to avoid failed assumptions as to the logic each model uses to transition stages.

The resulting data is rather interesting. And I think it raised a couple questions:

The Goodman Deluxe (D) series was dropped in 2017 and only the G and A series remain today. Could the current 18 seer goodman really be 35% less efficient than the amana?
Somehow the 16 seer GSZ always performs considerably better than 18 seer GSZ? Even the 14 seer performs better, but admittedly that is partially a product of the 14 seer being single stage and me only allowing the 18 seer to run in its high stage.
This begs the ultimate question.. Do we feel the heating data table that manufacturers provide us is accurate? If so, then it would appear that at least daikin may be gaming the system and tweaking their models to perform well in the standarized seer and hspf testing at the sacrifice of general overall practical efficiency(aka 16 seer is actually better than 18 seer in cold temperatures).