You actually do not need to know the consensus rules to determine the PoW chain with the most work. Simply by understanding the hash function and difficulty, y

You actually do not need to know the consensus rules to determine the PoW chain with the most work. Simply by understanding the hash function and difficulty, you can calculate the total work of any PoW blockchain. This provides some amount of trust that is very difficult to subvert. You only need to know the consensus rules if you want to be a miner on the chain.