If you like biology you should study it. If you don’t like it, don’t study it.
Take it from a medical student (USYD Class of 2025) that there is no additional advantage to studying biology in the HSC to getting into medicine.
Having studied biology will help you in your medicine course as you have helpful background.
But in terms of getting in, the most important thing is getting high marks. And the best way to get high marks is to like the subjects.