I read that too, and I wondered about it. The passage being referenced is in the Darkroom Cookbook, 3rd ed., pp. 33-35
He says there are three kinds of B&W film:
1. Old-style emulsions that rely entirely on silver halides to form the image, e.g. Efke 25
2. Conventional grain emulsions that utilize color dye sensitization to form the image and thereby reduce the amount of silver in the emulsion, e.g. Tri-X or HP5+
3. Flat-grain emulsions, which utilize even less silver, and even more color dye sensitization, e.g. Tmax or Delta
The implication is that 1 is the best, since it has the most silver. He also says 1 is the most sensitive to expansion and contraction, 2 less so, 3 the least.
I have not read that perspective elsewhere.
I believe it is the quality of the final image on the negative that counts, and after fixing most of the silver gets washed away anyway. So it is really the quality/quantity of the silver that gets left in the final image that matters, isn't it? Modern films are less wasteful of silver in this case.