I agree it is a common wood chisel. Is he using it as a skew or a scraper? It is not presented at the normal scraper angle, but it also doesn't look to be presented as a skew. I think that presentation is likely not the safest practice. I picked up some used tools at a garage sale or auction years ago and I believe several started life as chisels and are now scrapers. Carbon steel so I don't use them much at all.
I remember him saying in an older video that regular wood chisels are what he learned to turn with. He acknowledged that it isn't the best approach, but it's how he learned, so it's what he's become comfortable with. He doesn't do a lot of turning. Mostly stuff like this - a round part for a larger project.