Your point about studying code & improving it in isolation is good. The weakest part of the analogy, in my opinion, is that in tactical chess puzzles there's actually a right answer.

On the other hand, if you have a chess puzzle but not its answer, you can still practice recognizing the tactical situation (hung pieces, checks, forks, pins, etc.) That's closer to what I was suggesting, and I still think it's useful: learning the jargon first, and then reading code and taking the time to describe it in terms of that jargon. The purpose isn't to "discover things you don't know", it's to concretely drill and internalize things you do know.