Does the rule of United States v. Mezzanatto preclude application of the contractual principle expressed in Brooklyn Savings Bank v. O'Neil?

QUESTIONS PRESENTED 1. Does the rule of United States v. Mezzanatto, 513 U.S. 196 (1995), that a statutory right is waivable in a plea agreement absent an affirmative indication by Congress, preclude application of the contractual principle expressed in Brooklyn Savings Bank v. O’Neil, 324 U.S. 697 (1945), “that a statutory right conferred on a private party, but affecting the public interest, may not be waived or released if such waiver or release contravenes the statutory policy”? 2. If the contractual principle from Brooklyn Savings Bank is applicable to plea agreements, is a waiver in a plea agreement drafted by the Department of Justice contrary to the statutory policy of the First Step Act, which removed the sole compassionate release gatekeeping powers from the Department of Justice due to its poor administration of the compassionate release program in the Bureau of Prisons? i