There are several techniques there -
excentric chuck,
cantilever mounting of the mandrel (but with single piece of wood)
power sanding.
The excentric chucks are pricy -- $300-$400 new. There are a few on the market from Australia, England, France. However, you can use a fixed plate for offset 3 point turning (variant of the pendant turning fad) or with multi axis - 3 or 4 blanks mounted into a fixture and one face turned on all at the same time.
Cantilever mount does require some good skills in tool use to avoid bending steel.
Power sanding is not the norm, but I do use it with some pens with tight tolerance situations and a need to remove a bad spot. I use 1 inch rounds in those situations. It requires a bit more care and some practice, but avoids the concentric ring effects. I sometimes use that with pens, especially with some special woods.
The author of the video has some good skills and good gear. Watch and learn grasshopper -- which was the ooolllldddd time method for the apprentice -- watch and learn.
