That is utter nonsense I am afraid…
First lets clarify the purpose of this endpoint. This endpoint can be used to retrieve a candidate key-block, i.e. a keyblock that can be mined upon.
This key-block is tied to the node at hand, the reason for this is that the nodes use throw away key pairs for micro block signing. I.e. each node generates a key-pair, and adds the public key to the key block it is trying to mine. If the node is successful in mining the corresponding private key is used to sign the micro blocks. After a key has been used for a generation another one is generated. The benefit of this scheme is that you don’t have to keep the signing key very secure since it is only valid for one generation. The mining (+ fee) reward is sent to the
beneficiary that is separate from the
miner in the key block.