I don't think so. Scaling definitely exists but i do agree with the rest when it comes to students choosing subjects based on scaling. Students should choose their subjects according to their likes not scaling. You can do low scaling subjects as long as you maintain solid marks if not, no matter what people say, scaling will effect your end result to a certain extent. I highly doubt that the guy from BOS told you that there is no such thing as scaling because Sydney Morning Herald frequently releases subject scaling related articles when the hsc draws nearer.
Scaling shouldn't impact on your subject selections too heavily. If a person believes that they are capable of doing say 4u math then by all means they should do it but no one should choose it purely based on the scaling. A lot of people forget that scaling can bring a both positive and negative result to your uai. Like all subjects - if you perform well in them, you are scaled up & if you perform poorly, you are scaled down. I know plenty of people who had done 4u math and english and ended up with uais in the 60s and 70s.
Obviously someone who gets a 60 in general math (which is a fairly simple course) will get scaled down more than a person who gets 60 in 4u math, which is a lot harder and involves a lot more time and study.