I don't think you'll have major problems with either a Windows or Mac laptop.
Realistically, most stuff in CS will probably need/be simplest with Linux, so it will be less hassle to just setup Ubuntu or similar in a VM rather than mess around with Windows Subsystem For Linux or Mac OSX's slightly different flavour of Unix. You'll be able to do that in either Windows or Mac OSX.
The point of that person's opinion on Reddit is that Mac OSX is Unix derived, so closer to the Linux you'll be using on the labs. That's true, but it's still not Linux and I doubt the average OSX user will build much Unix profiency just through using OSX.
I don't know the whole UNSW course very well, but it's also pretty common for embedded software stuff (especially from 10+ years ago) to only support Windows. I believe UNSW definitely covers some stuff with MIPS, and that might be the case there. But once again, I think not having a Windows PC in that case would be a minor inconvenience as opposed to something you base your whole laptop decision on.