I can see a seat in the picture, so you would expect that driving it by hand to be a fallback. It isn't ideal, but might be a good enough solution for their user base.
Any farming operation where humans might possibly be around this won't work for. We want this to be full autonomous, but the technology isn't ready.
The primary purpose of this is to target great engineers (ie the people who read hacker news) with the idea that we are an exciting company to work for. I personally have some code in this tractor, and I know the people who work on it. We have lots of open positions, the jobs are fun (as hard as any other engineering of course), and you might want to join us.