That time dilation near a rotating black hole depends on Kerr metric parameters is a matter of definition and standard relativistic mechanics, requiring no external citation.
The claim states a direct mathematical and physical consequence of the Kerr metric, which describes rotating black holes. By definition, time dilation effects in this spacetime are governed by the metric parameters (mass and angular momentum). Following the instructions for trivially true or definition-based statements, this is classified as COMMON_KNOWLEDGE, and no citation is needed.