Not the replied-to user, but I also wasn't aware of the mathematical definition and my understanding of idempotency was that the main point was that performing

Not the replied-to user, but I also wasn't aware of the mathematical definition and my understanding of idempotency was that the main point was that performing the same idempotent operation multiple times wouldn't make a difference in terms of __side effects__ (for instance, not charging a user twice when accidentally submitting an idempotent request twice).