[quote=“Charlie Jack”]
[quote]Functions of nouns
ADJECTIVAL[/quote][/quote]
Yes, nouns, like adjectives, verbs, and more, can modifiy the meaning of nouns they are placed before, but that does not change a noun (a word of a certain class) into an adjective (a word of a differenc lass) - the term “adjectival” (not a word class but a function descriptor) takes care of that, however: as we see here nouns can have an adjectival function… 
and
[quote=“Michael Swan”]378 noun modifiers
It is common in English to use nouns in a similar way to adjectives, to modify other nouns.[/quote]
My point. And this feature is by no means unique to English… 
[quote][…] coffee beans […]
Swan says that coffee modifies beans in that construction.[/quote]
Yes, coffee beans are a subset of all items one might refer to as beans. Or, said in in a different way, the expression “coffee bean” is narrower in its meaning than the word “bean” by itself.
[quote=“Elsewhere I wrote”]Nomenclature and concepts differ from place to place, and they change over time. I think it’s a good thing to have some kind of nomenclature, though, but in grammar, differences in names or even concepts don’t matter too much to me, [color=#000080]as long as I have the opportunity to get on the same page as the person using them[/color].
But I suspect that some folks here rather enjoy not being on the same page.[/quote]
It rather seems more unavoidable than enjoyable…