Supervisor may avoid of higher rating to the subordinate in terms of HR Performance Management. Is it TRUE or FALSE?

false 

This will never be true unless the subordinate is an under performer or the supervisor doesn't upkeep professional ethics and values

It is totally false.

False,,,,,,,

Unbiased supervisory positions will never do such falsifications to support organizations ethics and culture.

The statement is not correct as far as a model supervisor is taking the steps.