I mean the plow is behind the tractor ..?

Sure you might drive on it afterwards but from my experience a field is not a dry granular road surface like a gravel road. There's also way less traffic, the fields gets plowed frequently and sees almost no traffic. It also turns wet from rain and water and "moves" naturally.Completly different from a gravel road. On top of that the wiki article even recommends "plowing" the road to remove washboarding.

I am not saying that you are wrong because I am geniuenly interested to learn about this, i never thought about it before. But the arguments presented still have me sceptical. That being said the general idea you presented makes perfect sense, of course you'd want to "squish" the ground as little as possible with the tractor. I can understand that without any science.