not new.. but just done differently than the old way

year ago people used to create 1 of 2 multisig where the first key was the spender key, and second was just a hash of a message which was privately communicated thus proving the message was part of the multisig address to then know the purpose of the multisig address

the rest of the world just seen multisig pre-spend. and  legacy addresses +1signature post spend.. but the people involved also had secret knowledge of the message of the second legacy addresses hash