The Classification and Rating Rules document of the MPA details that movies may include unrated material like deleted scenes, interviews, commentary, etc.
"Classification and Rating Rules," The Classification and Rating Administration, filmratings.com, accessed November 30,2022
G. If a rated version of a motion picture is distributed in the home entertainment market with audiovisual material in addition to the rated motion picture, such as deleted scenes, interviews, commentary, bonus material or other similar materials ("unrated content"), the distributor must comply with the Advertising Administration Rules with respect to such product and must include on the packaging of the product the following legend: "This product contains the _-rated motion picture and additional unrated material" or a similar legend acceptable to the Advertising Administration.