I'm looking at their recommended cut and IMO it is a broken bone waiting to happen. You really have to think of that tree as a giant spring. A lot of stored energy the way they are cutting.

I wouldn't do it, not on purpose.

I've seen 6-10 ton trees pop an jump, spring loaded like that. Especially if they have fallen across another tree making a fulcrum.

I watched a guy get flipped 10-15 yards through the air dealing with tornado damaged forest. Made me a believer.

When we are cutting, the first order of business is to release the stress. Not to fell tress with built in stress.