Right to repair doesn't change any of that. Farmers were adjusting that screw anyways, that was the entire point. I'm not mad at farmers for doing it, I'm mad at John Deere at cheating the system.
It's not John Deere that was doing that, just some Korean companies exploring the opportunity and importing to the US. John Deere is located in the US and too afraid of the whimsical interpretations of regulators to try something like that, I think.
There was no "screw" for the commercial John Deere tractors with emissions controls, that I know of, as that was locked down to prevent "repair."
The point is that when the firmware was locked down, it was vastly more difficult to bypass emissions restrictions. I'm not sure what you mean when you say John Deere was cheating the system. Arguably they were taking compliance more strictly before this ruling.