Leave it to Singapore to worry about this.
I'd love to see the attendant's pre-flight pantomime imparting this bit of information. It would come just after the pointing out of the emergency exits and before the instructions on use of the oxygen mask.
The brochure illustrations would be a hoot, as well.
Perhaps airlines could make a little extra revenue by providing the appropriate privacy arrangements for 1st class passengers.
Remember when Red Skelton, dressed in drag as a stewardess, got in trouble during a TV skit by asking the passenger if he preferred "some of my TWA coffee or my TWA tea"?