Yes, but who says the more you write - that every extra word will be 'quality'?
My point is that once your goal is "omg i must write at least 1100", then you're pretty much inevitably going to write irrelevant fluff that will boost your word count sure, but it won't be quality material.
Why? Because in the HSC, it's a pressure system - if you only have some material, and you try to draw it out and expand it further than it should be, then your essay quality is going downhill...
Now you could have lots more material, but you have to answer the question - so if you're going to try to boost your word count by putting in that extra point which doesn't really answer the question - again, your word count goes up, but your essay quality goes down.
I'd rather have a shorter essay that answers the question, rather than a longer one which has weak points and too-extended an analysis because "I have to get 1100 words" or whatever.