Well that's actually wrong... people who wrote 2 did fulfill requirements of question, the question said refer to set text and ONE related.
writing 2 means you did fulfill requirements of question but just went further than what is asked.
Just like for short answer responses in any writing-based topic.. if it asks for an example of something, and you decide to not only define the question, but write your opinion on it, and then provide 3 examples with analysis.. Yes you are wasting time, but no they're not going to give you a 0, if you fulfill the requirements of the question somewhere in the verbal garbage you will be awarded full marks.
That said, most people who wrote 2 wouldn't have gone into the depth that someone who wrote one would have, so that would detrimentally affect their mark.
Me, I wrote 16 pages for the essay. I did 2 related, but I'm pretty sure that either of those related are in a lot more detail than what the majority of people who even wrote one would have gone into, so i don't expect it to affect me much.
and yes.. i am getting arthritis early. my wrist is killing me.. 2 weeks of hell to go...