Earlier quoted context omitted.
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.
posit: are these considered 'road vehicles' in the same way that a car is?
Of course the government exempts itself from this because they know all that bullshit of "it's just as reliable etc" is trickery. It's common to buy previously government owned deleted vehicles, because the people working in federal government don't want to eat the dogfood the plebs do, and AFAIK if you buy it from them then you're allowed to have it.