Re: green or yellow as a third primary
I suspect the fundamental problem is the nonsensical way we teach children about colour.
For example, “Roy G. Biv” is a lousy way to describe the colours we see, because it conflicts with colour nomenclature. Either it omits cyan, or calls cyan, 'blue' and blue, 'indigo'. It also completely omits magenta, since it only addresses spectral colours.
Magenta is missing; magenta is the emission of red and blue-stimulus photons simultaneously. This can also be accomplished by absorption of green photons from full-spectrum ambient light, which is what magenta ink does.
Until one understands colourspace, and how additive and subtractive colour work, and arguably also how colour spaces are defined, it's hard to generalise laws that depend on colour perception.
Simpler, more abstract ideas about colour lead to design decision ambiguity. Individual designers don't follow consistent rules. Two designers, working independently on the same assignment, will have different final results. That's okay in my books.