I said this 30+ pages ago, and I see people are still discussing this.
An SRD is a System Reference Document. It is not a play document. It is not an "interest" or "history" document. It is a Document that References things in the System. By definition, there shouldn't be any References that aren't in the system.
There can be only a single correct answer, there's no debate and there's definitely not 34 pages of debate. Anyone who thinks it should be in there is simply mistaken about the purpose of a System Reference Document, thinking that someone things that are not References to the System should be in there for other reasons. But, as in the title, the only reason to put things in the SRD are References, and those References are to the specific System it is referring to. System Reference.
If I have a 2022 Toyota Camry, and someone was creating an SRD of it's manual, it shouldn't have anything in it from my other vehicle, even if that's convenient to me. That 2022 Toyota Camry SRD wouldn't refer to manual transmission, because even thought that was offered in earlier editions (snirk) of the Camry, 2017 was the last year of it. And it definitely shouldn't have anything from the Model T, even though that's an important ancestor. That's because a, say it with me, System Reference Document, only References the System it is referring to. By definition, it doesn't reference anything else.