But the food needs (and other needs) have expanded 10x. It makes no sense to look at the absolute numbers instead of the percentage. If there had been no technological advancements at all, the workforce would have still expanded (in absolute numbers) to match the population.
Without machines and technology, we would need far, far more people today in agriculture. The need for all those jobs has been destroyed by technology.
When one job becomes obsolete, this frees up labour and people gradually move to other jobs. This increases production, since we're still producing agricultural products (using fewer people), and there's more people now producing other things. Agricultural jobs were destroyed, but there were always other jobs people could do, that weren't done before simply because agriculture sucked up so much labour.
This pattern will continue for a while. When human labour is no longer the best tool for one job, that labour will be reallocated to something else. There's still plenty of things we'd like more of.
But the video is talking about what happens when humans are no longer the best tool for any job. It's happened many times in history that some job has become obsolete. We haven't yet made a machine that's better than humans at every job.