I’ve been going through a Nihongo Kyoshi grammar deck I found recently and maybe the way they format it could be helpful? The front side will present 3 random sentences from 15~ example sentences with the grammar point at top. Then the back side gives an explanation of the grammar point along with all of the example sentences.
I don’t remember the definitions verbatim but I usually pass a card if I can understand its meaning/usage in the example sentences.
Seconding the above post, I feel that example sentences would be an absolute must when making a grammar deck, so that you can see each grammar construction in context. Multiple sentences would probably also be good when a grammar construction can have more than one meaning/usage.
That’s probably the approach I’d use if I ever made a deck based on my grammar resources, like for example Cure Dolly. She provides a lot of sample sentences in her lessons that make good candidates to include in cards.
I’m a bit uncertain about the value of grammar flash cards. Definitely for more common, foundational grammar (roughly, pre-N1) I think it appears so often anyway that there’s no need to take the time to SRS it. I did SRS some N1 grammar as part of JLPT prep, and the approach I used there was cloze-deletion cards in Anki, so the prompt was a sentence with a chunk cut out plus an English hint of the thing to fill in. But this I think only works if you do it for a limited number of cards, otherwise there are too many possibilities for the phrase to fill in. I also think it works best for the kind of time-bound purpose like test prep, because after a while you start to remember the required grammar item just from the example sentence, without going through the ‘meaning → grammar’ step you’re supposedly drilling.
On the back of the cards I put the filled in sentence, plus a brief English summary of any important non-obvious things. Because I only did this for grammar I had already learned outside the SRS, I only needed hints to remind me of that sort of thing, not a complete explanation.
I know exactly what you mean, and yes, I’m using “grammar” in the usual Japanese-as-a-second-language extended sense which covers a lot of things that could be classified as idiom, vocabulary, common sentence patterns, etc. But from a technical point of view, the fact that 〜ず is N2 is a counterexample to your thesis