What behavior can’t be deduplicated, if deduplication is defined as: first call executes, subsequent calls noop? I don’t see why idempotent functions couldn’t

What behavior can’t be deduplicated, if deduplication is defined as: first call executes, subsequent calls noop? I don’t see why idempotent functions couldn’t also be deduplicated In which case, we’re really just back to “idempotent” and “not idempotent” (knowing that you can turn any operation idempotent, by using this one trick..!)