Ok, let me try to sort this out. I have heard of "silver rich" enlarging or contact papers. The best known example is the POP by Chicago albumen works, where at some time they "claimed" their paper produced better blacks because of the extra silver. This claim was later adopted by Forte. Dr. J. Henry in his book controls in black & white debunked this theory by making measurements with a micro densitometer and ploting the results vs a "normal" paper, where he shows that "silver rich" papers do not have any advantage over any other papers as far as obtaining greater Dmax. IOW they DO NOT give blacker blacks.
Some people, Adams among them hypothesized that "older" films gave better results because they had a higher silver content than "modern" films. Among the supposedly better qualities was better expansion and less blocked highlights. The best known example is super XX, of which Adams was very fond. IMO this anecdotal experiences are due to the less than perfect antihalation dyes used at the time, where the "modern" films were more suceptible to problems caused by inadequate antihaltion dyes.
As Sandy mentioned, the effect of pyro or tanning developers occurs in the gelatin and not in the silver, although the presence of silver causes an enhacement of the stain. The trick as Sandy and others have done is to formulate a developer which has little effect on the gelatin but is augmented when "exposed" silver is present and aids the tanning developer into forming a stain. These we know as proportional developers. GIven the "correct" formulation proportional developers like Pyrocat HD can be made to behave like other pyro developers and produce an overall stain, but this has less to do with the amount of silver content than with the formulation and action of the main developing ingredient that is pyro or catechol.
Unfortunatelly for Aggie she got caught in a debate which probably she was not aware but which people who have been doing this for a while know to be less than truthful. ALthough the term "silver rich" is present in the photography literature, it is essentially meaningless as it has not been proved that silver content can be connected with "better" negatives or prints, and most of the anecdotal obesrvations are many times due to other factor than silver content.