It's virtually impossible to make out while whistling and clapping. Thus, the adult can avoid akward face-to-face supervision by being in a contiguous room and still hear the whistling and clapping. Of course, that's all in theory. in practice is enough to have an adult saying that to create awkwardness and stay away from smooching and hugging.
Mamá: Los dejo solos en la sala, pero... chiflando y aplaudiendo, ¿eh?
Mom: I leave alone in the living room, however, I wanna hear you clapping and whisteling, ok?
This couple took it literally.