Because:
a) It does not really matter what is there, as the ignition is controlled by idle pid at low load
b) They probably did it so that there is not a big ignition jump when transitioning from normal operation to idle controller.

To answer that question the car needs to be put on a dyno in steady state and go WOT and hold it at the fixed RPM and see if the engine ever hits those load cells.
It can be that it does not and they are simply extrapolated from the data that is there.
It can also be that it does and there is knock.

You are going down a very bad path. Playing excel spreadsheet with ECU file.
It's not a computer game, there's an engine working there, and you must understand how the engine works first. Not blindly stare at the numbers.

If you know how the engine works then the answer to your questions is completely trivial. I recommend reading a few good books about the basics of combustion and engine management to give you a base to work from instead of playing excel guessing games