That’s not silly at all, a lot of people use Anki for things like that. I’ve seen a couple of premade decks but I would avoid these.
When it comes to keybindings its better to make your own deck otherwise you end up learning a load of bindings you’ll never use. I like to add them as and when I need them.
It's not always that easy to find - even with C-h a or C-h m, etc.
But the bigger benefit is even knowing that feature X exists and there is a key combination for it. I found flash cards useful because I would get an occasional "reminder" that X exists and I should use it more often!
A trivial example: flush-lines and keep-lines. I never knew these existed till I read them somewhere. I put it in my flashcards, and over time I would remember its existence and use it more and more.
You could also try searching for "apropos" with apropos-command to find other related commands.
Emacs is vast and deep and there's a lot to learn and remember.
It also serves the same purpose for key-bindings and functions in various modes and packages.