Maybe it's because the robot needs different amounts of time for different patches of soil? As in, it kinda needs to go its own pace to a) ensure it has enough

Maybe it's because the robot needs different amounts of time for different patches of soil? As in, it kinda needs to go its own pace to a) ensure it has enough time to detect and kill all weeds (which depends on weed density, presumably - the video shows it only killing one at a time) and b) maybe it has to stop to ensure it hits the right thing because it can't handle moving targets (not clear from the video)? No idea if this is something that modern tractors could accommodate already or whether it would need some annoying human-in-the-loop stop and go.