What Gerald wrote was in the context of experienced users giving advice to novices, who more often than not end up in confusion and despondence. You probably know how to filter advice based on whence it came, but many inexperienced people can't, and don't know the APUG community. It took me two or so years to filter out the fluff. And you ought to understand that Gerald wasn't imposing his view of the photochemical world on you per se. He was merely pointing out that we are not doing newbies much of a favour by inundating them with conflicting advice and data, and he provided some perspective on how development and exposure are related to negative properties. I happen to agree with his approach, as it helped me to understand what I was doing and how to improve. And despite me being quite experienced by now, I tend to stay very close to manufacturer recommended development times and rather change the exposure to put the tones where I want them on the scale. This gives me a "negative for all seasons", which will scan and print well, on different enlargers and in different scanners. What I can't then compensate for with variable contrast printing and some dodging and burning usually isn't worth doing in any event.
Mixing different developers may for some unknown reason still prove to be useful. But there is no manufacturer support for such an approach, and no scientific proof that it solves a known problem better than other known solutions. It is not predictable, and not well studied, outside of the few casual experiments that some have done in this regard. Yet, it does not prevent anyone from trying it himself. In the context of helping newcomers come up to speed, it is spectacularly bad advice to suggest mixing developers, though. For me, it falls squarely in the arena of alchemy, not science (as yet). Unofficial developers such as Caffenol and its many variants are also in that category, but at least there is a fairly large user base with enough data to benchmark against that Caffenol can be considered by new users under the "use with caution" warning. I toasted several films with Caffenol stand because I did not happen to read that it does not work well for TMax 400, for instance. I was very annoyed afterwards, since the info was hard to find and I only knew to look for it after I suffered the consequences. This is the problem with being inexperienced and not using manufacture supported products and methods. No one to help you, since the manufacturer cannot cover usage outside of specification. And the web is a mine field.
And for the life of me, I can't figure out what Leica and Kodak have to do with what Gerald wrote. There is a clear distinction between what you call "Kodak lies" vs industry guidelines for the best compromise result for many different lighting conditions etc. Since the latter is based statistically on the best chance that an acceptable image would result, it is not dishonest. What other approach would you have suggested under the circumstances that prevailed at the time? I do share your dislike for the Leica way of preaching certain fiction as facts, but I don't see the link to Gerald's post.
I would like to add a caveat for the newb that consistency is one of the best teachers when it comes to photography and printing, as Gerald said in the fat part of the OP. 
