It's pretty silly to call it cheating. If the information is there, it's likely going to use it. "Cheating" is just a human value put on top to try to force an LLM to adhere to your wants.

This makes no sense to a process designed to explore and find solutions. If you want an honest test, it's on you to build a proper test - not force the machine to pinky swear that it'll stay away from "forbidden" information.