Yes, that’s my criticism as well: a single adj category has no meaning because there is two of adjectives in Japanese, one with verbal trait, the other acting more like nouns. The difference can and needs to be addressed in a grammar.

The grandparent point about recursive rule(s) is valid however and their easiness is one of my favorite things in Japanese grammar.

Anyway, the problem seems easy at first but it’s totally possible to vaste hours perfecting a grammar that still doesn’t capture frequently occurring construction (been there done that).