That is a better example for sure. I still think there are issues since it could be somebody other than one of your parents knocking (including multiple people)
I think the better example would be when you know there is only one person. Person 1: "I went to the movies with a friend". Person 2: "Did they like the movie?"
This still has the issue about talking about somebody who is not present. Many people are advocating for using they/them when the person is right in front of you.
I think the better example would be when you know there is only one person. Person 1: "I went to the movies with a friend". Person 2: "Did they like the movie?"
This still has the issue about talking about somebody who is not present. Many people are advocating for using they/them when the person is right in front of you.