I understand that. But ZS has no real place in the discussion of film and paper design - even at the most basic level. One would hope when it comes to the why and how of film and paper design, students would become acquainted with real sensitometry (including at least some basic scientific method fundamentals). Once you get into that, you have less and less need for a simplified, non-standard model like the ZS which would lead to all sorts of problems when it comes to testing and coming to meaningful conclusions about the properties and characteristics of the materials.
I just don't think the ZS has anything to do with it.
Perhaps we need to step back a little, read Adams carefully, and evaluate the ZS in the context of what it is and is not. If one studies exposure theory, speed methods and tone reproduction, the shortcomings and inaccuracies of the ZS become fairly obvious. But few people want to study sensitometry, so the ZS provides an alternative - a reasonable, simplified framework for exposure and development of the negative to support visualization. It isn't meant to be more than that. As I've said before, it's the many bastardizations of the original Adams/Archer system, the so-called improvements, extensions and other gimmickery that give people the impression it is "hard core" sensitometry, and imply a level of precision it cannot deliver.
Everyone wants to sell their own ZS book. This has done a real disservice to Adams in my opinion. And I say that as someone with an interest in sensitometry, tone reproduction theory, speed methods, test design and methods.