Yes, the green belt has very little to teach, but the white belt can only absorb very little. If anyone is the theif, it is the sensei, who steals personal training time from his green belt when he/she himself could be doing the teaching. However, IMO, teaching is a valuable opportunity for learning, and should a company training in an appropriate way. Teaching must be learned, and the ego does not simply vanish but must be defeated over time. New students suffer your egotistical teaching. In exchange, they learn from you. They suffer your weakness, you suffer theirs. It is a fair, harmonious trade in from which both practitioners can draw strength and develop a good training relationship.
The authors description makes sense, and restates the old "empty your cup" argument fairly well.
Sounds like a person who treats the dojo like a gym. They have a right to do this, IMO. Being bitter about it helps noone. A dojo can be different things to different people, as long as there are no gross violations of conduct or respect.
The authors conclusion is not very readable.