I'll agree that roadways have much more to do with avoiding traffic, but I don't think that the restrictions on vehicle operation or avoiding hazards on the terrain or having to understand and plan according to layouts devised by and primarily for humans is substantially different between the two, but rather, a difference of parameters. (Farm equipment maintains a lower speed and for a different reason, but still has to monitor and obey rules about maximum speed under various conditions, for instance.)
I think you're underestimating the degree to which the two tasks are fundamentally the same.
Coordinating with other moving equipment I did not address, because that is too broad a description. As far as hazard avoidance is concerned I don't know the state of the art for farm equipment, but I don't think they are as focused on fully autonomous operation, which has been the goal on the transportation side for some time now. In any event, there is obvious overlap in a number of areas, but I simply don't think the premise of the posted article holds up. Farm equipment is not the "real revolution" in autonomous transportation. It's merely one area in which some of the dependent technologies have already seen the light of day.
Nope, they don't need to worry about those things. Self driving cars and tractors adhere to ISO-25119 and within that, tractors adhere to agricultural performance level which doesn't have the same risk. Self driving tractors are required to have an operator in the cab and they are not allowed on public roadways with "auto guidance" engaged.
I work for Case New Holland - John Deere competitor.
That's a lot different than having a car which can at 70mph successfully swerve enough to avoid a wreck while still not swerving so far as to cause another wreck.
Were I in need of a self-driving tractor given the much lower speeds and whatnot I might be much more willing to accept a fairly primitive autopilot rather than something truly self-driving. Freeing me from needing to constantly be on the alert to keep a combine from straying from the optimal path is far, far more important that something that'll drive itself from the barn to the diesel pump and then onwards to the field. Were I wealthy enough to afford so much land to where owning such a vehicle was necessary then either driving it myself or hiring someone else to handle that would be entirely reasonable.
Automated cars can already do this far more reliably than your average driver.