I will be annoyed if people who made this mistake still get credited. If you have rehearsed an answer to the extent where you expect to be able to regurgitate it onto a piece of paper whenever the word Birling comes up, and not have to look at whether it said Mr or Mrs, you deserve whatever you get. You clearly don't have a sound understanding of the paper if you didn't believe you would have to learn about other characters. As someone who to be honest only expects a Grade 6 despite having a good knowledge of An Inspector Calls, I don't want to get a sub-par grade due to someone 'misreading' the question and getting a number of marks which they could never have attained if they spoke about Mrs Birling, especially as I could probably have got at least 25/30 marks if I wrote about Mr Birling, and yet had to choose to write about the Inspector instead.
Obnoxious rant over.