Semantics. Some obvious truths presented, but mostly just a person who likes to listen to his own mastery of the language.
The author argues that "expansion" requires an increase in mass, while deformation may occur while mass is decreased by disintegration of the projectile (jacket, core, or both). An obvious truth, but presented in a manner that is well outside the usual applications for sporting or defensive ammunition usage.
Just as obviously, a projectile meeting resistance begins to decelerate, thus deformation slows and halts at a certain point. I would argue that this points out one of the fundamental points in favor of "expanding" bullets, which is limiting penetration by quickly shedding energy in the target media.
It has been a long time since I flunked out of barber college so I probably shouldn't get involved in deep discussions with physicists or professional engineers. I'll just say that sometimes expanding on the truth is another way of piling up the BS.