In terms of net inputs vs production he's likely correct. You use less energy when harvesting by hand (i.e. no petroleum for the tractors, etc) and yield per meter is greater because you have a more granular control over each piece of produce so less gets crushed by an inaccurate combine for example. The problem isn't strictly one of efficiency alone however but rather of
scale. For comparison compare farming to construction, if you're making a sand castle building one by hand is more efficient than using a machine for various reasons. But once you're talking about building a larger structure like a skyscraper than doing it by hand is crazy talk even though on a micro scale it's more "efficient" you don't want to wait hundreds of years for the more "efficient" hand construction that using automation could complete in a single year. It makes no difference if you'd be more efficient at farming by hand if all you can farm and harvest is a half-acre plot. To use made-up numbers, 90% efficiency at non-automated farming on a half-acre gets trumped pretty convincingly by even 60% efficiency using automation that allows one to farm 1,000 acres.
https://veganorganic.net/2012/06/what-is-efficient-agriculture/