This, as others have noted is not a right to repair, it's a right to
pollute.
There's a push for agricultural right to repair.[1] That falls under the Federal Trade Commission, not the Environmental Protection Administration. That's about parts and tool availability for the whole machine, not just the Diesel power train. This new announcement has zero effect on that.
Here are the controls of a modern John Deere combine.[2] Very little of that has anything to do with engine control. It's being able to fix that, and all the sensors and actuators connected to it, that's important. Diesels are rather reliable by now.
[1] https://nationalaglawcenter.org/ftc-files-suit-against-john-...
[2] https://www.deere.com.au/assets/images/region-4/products/har...