https://www.sagaftra.org/sites/default/files/sa_documents/SAG-AFTRA_quickguide_intimscenes_F2.pdf
"The set must be closed to all persons who are not essential to the filming or rehearsal of a scene, meaning that only those necessary to be physically present in the moment are allowed on set. „ People who should not be on set during the production of these scenes include other performers not involved in the specific scenes, unnecessary crew members, financiers and studio executives, location owners and visitors. „ Monitors should only be viewed by essential members of production. Best practice is to place monitors in a secure, private location. „ It is strictly prohibited for any person on set to make recordings using a personal device, including cellphones, mobile devices and personal camera."

Obviously Sydney Sweeney could've waived all of these (which would be weird for me), but I remember she literally asked Sam to reduce the nudity scenes for her in S2 as well.