The scene early in the play where Gilda has a bath in a full length deep bath indicates how false this play - and this production - are. The character lives in the cheapest attic apartment, the "grenier" and she has a indoor plumbing and a full bath. No at all. People who lived in the tiny one room flats used the public baths, or they had a sit-down bath which was not connected into the mains water. The production designer had no idea of this fact of Parisian life.
It's not just this error; humor and social mores change with time and that also includes drama. Coward's play is not an authentic portrayal of people in Paris, rather, it's how his English middle class audience perceive those types of people. It doesn't have to be true because it's based on a perception.
As the play, and this is also true of Coward's other works, is not about the people in them, but the audience, as Coward played to them, his paymasters, he never rises to much at all as a writer. He was a mediocre, formulaic stylist with an easy appeal, but which fades very quickly.
The skill and faults are evident in this play. The characters exercise their wits as they strike dramatic routines based on misunderstanding, or ironically use a proverb, which is turned around and ridiculed. They extemporize on an idea, love, with neither facility nor much insight, as they keep to the strict limits of the audience's own conception of the idea. There is never anything genuine in the exchange because the playwright has nothing to offer, but he can make it seem very classy and witty, for a second or two. It is a long-winded and self-indulgent as the actors laugh at their own jokes, at their own past when they did something outrageous. It is tedious once the form is understood.