It says: "All self-propelled equipment shall, when under its own power and in motion, have an operator stationed at the vehicular controls. This shall not prohibit the operator occupying or being stationed at a location on the vehicle other than the normal driving position or cab if controls for starting, accelerating, decelerating and stopping are provided adjacent and convenient to the alternate position."

So you do explicitly need to be physically on the vehicle at all times while it's moving.

It has further rules for remotely operating "Furrow guided self-propelled mobile equipment" (which is not how modern autonomous tractors work), but even for those you need to be actively watching it and have immediate access to steering and braking controls.