I agree. I wish the whole length == intelligence thing stopped after high school. In high school the teacher sets out a length that your essay needs to be and the student mindful of the length requirement fills the space with a few bullet points and copious amounts of BS which translates to a lifetime correlation for most people that length == A paper.
I think Pascal said it best: I have only made this longer, because I have not had the time to make it shorter.
This reminds me of a great essay, "How to Say Nothing in 500 Words or Less" - http://www.apostate.com/how-say-nothing-500-words. I think this nonsense should stop way before high school. I still remember the SPERM formula from my social studies class - social, political, economic, religious, and military. Pick three, write a paragraph on each, and stick them between an introduction and a conclusion (which is really an introduction rephrased). I learned more about good writing by debating various political issues on the gamedev boards I used to frequent than in any of my high school classes.
WEll, length == intelligence has been disproven by shamir and his paper about secret sharing. 2 pages of groundbreaking paper and the whole crypto world is shaking.
Most of the time, if people tell me to write more, I just ask them what they are missing, and either I can point them to a single paragraph where it is written or I need to write more, indeed. Most of the time, the other people give up and accept the short length after around 5-10 iterations :)
I think Pascal said it best: I have only made this longer, because I have not had the time to make it shorter.