The language matters, but your original guess was actually correct, you can do tricks with sha256 where you only end up calculating a fraction of the total double hash in order to get a pass or fail.

Modern bitcoin miners do a double sha256 hash and increment in just a little bit more than a single hash of work. The input is 80 bytes, which is two compression rounds of 64 bytes in sha256, only the data in the second round has changed (the appended nonce), so you don’t bother doing the first compression round again. With other quirks you can end up doing multiple hashes at once “asicboost” due to partial collisions within the input too.