>but he hasn't seen a specifically designed and tested harness that autonomously manages a crop harvester.

Eh, I'd say there is a lot more stuff like this being developed these days. Autonomous seeders are becoming more common and (semi-)autonomous tractors are in use.

I'd say a very large part of the in field work can be done now, and is using enhancements like vision models to identify potential problems that crop up to notify humans. It's when the machines have to interact in tight busy spaces or with non-farm traffic that control is handed over to a human.