More than enough comments about PPE and setting up that notch. They're valid enough. The worry I see is staying in the felling cut too long. Once it get's going, if you've set up the fall right, it should fall happy on it's own. Staying in the felling cut like that, reducing the hinge further once the tree has decided it's going down, not clever, no reason to do it, plenty of reasons not too - such as being well clear of it as it falls.
Still - only seeing one angle in this vid and no way of seeing what the whole set of the tree was - a shame, I would have like to have seen the whole tree. Would have placed the felling of it into better context.
My situation - certainly no pro. Got a wee little MS251, a lusty old 039 and an MS661. Harvest and process West Australian hardwoods for slab, dimensional, burl and of course firewood.