I'll have to agree with Blue suede, honestly I see it to be quite logical. Though I believe that the true importance is answering the question, as has been repeated and drilled into my brain by teachers everywhere. i.e. you could write a 20 paged essay and still not answer the question. It's actually a lot more frequent than you think, perhaps not at the extent of a 20 paged essay. Although quantity does play a small integral part in it, I reckon that quality (answering the question specifically) is the real point maker, I don't believe the marking criteria has bonus points for a lot more quantity.
If you had that much time to be trying to write length, it'd be better off to just stop and think about the question further, then take out the relevant pieces of information that you know that is related to the question, and then write as much as you knew about it, given that the information is relevant to the question. (they probably wouldn't need to know Shakespeares birth date, etc. unless you were talking about the time periods he lived in and what influenced his play, etc. again depends on the question)
This also catches out people like you who are planning on memorising essays, if the question is different and you just spam all your irrelevant information down. GG game over man better luck next time