Just remember year 9/10's what you do this year, what you are best at, will lead to what subjects you do for year 11/12
Make a wise choice, do what you like, not what scales and what not
It depends on what you hope to get out of the HSC. If your primary goal in the HSC is have a learning experience, then you are correct. However if your primary goal is to get the best possible ATAR, then you are wrong. If you want to maximize your ATAR, you must consider scaling. For most people who want high ATARs, scaling plays a role regardless of what they tell you.
That said, you definitely shouldn't choose a subject that is beyond your capabilities as scaling will do you no favors.
There is nothing wrong with choosing subjects based on scaling, it may not end well if they don't like the subject and are not willing to work in it, but it's perfectly ok to do it.
Really you should be combining the two ideas, to get subjects you enjoy which will help with it ATAR. For example if you really like history, but not maths, than instead of doing ext 1 maths, do extension history. It scales a little less but because you like it you might just get more marks out of it.