imo the biggest injustice is that too much of it is about writing speed
True, but it's your fault if you don't have the speed. The onus is on you to practice. With doing study, and writing heaps, comes speed. And if there's a genuine problem preventing you from writing quickly, special provisions caters for you.
You can't blame anyone else but yourself for not writing fast, as you can't blame anyone else but yourself for not studying the content.
If you argue that everyone innately has differing hand dexterity, meaning some can naturally write faster than others, and that is unfair, then you could,by the same logic, argue that everyone innately has differing intelligences, meaning some can naturally produce better answers than others, and is that unfair?
Perhaps the HSC is more comprehensive as it tests mental and physical ability.
Even if it was unfair that you need to have a speedy pen, what alternative do we have? Do you want us to telepathically project our answers onto the paper?
Life's hard, take a concrete tablet.
Writing speed is by no means "the biggest injustice". That label lies with the disparity in results between those from low and high socio-economic backgrounds, it lies with the exploitation of special provisions, it lies with the wealthier having greater access to resources and services.
Don't come to me with your pitiful pen woes and your hyperbolic rhetoric.