The measure of a truly good customer service is how it handles difficult customers. In this case the bar is much lower. OP asked a very simple question which can be answered quickly if the FA had any clue. Instead OP got a nasty sarcastic response.
I can't imagine if the same FA was on my flight back from SFO this last weekend. It was in a transcon J cabin. My seatmate asked a series of detailed and rather difficult to answer questions about the beef filet that they were serving. The FA handled it perfectly with clear and concise answers to each of the questions. When she didn't know the answer, she simply said I am not sure but I can check for you. Now that's the type of customer service that we should be getting consistently.