Was about to pull the trigger on this one before I noticed that at the bottom the system requirements says Mojave (OSX 10.14), but near the top it says anything from OSX 10.11 onwards.

Can anyone confirm if this works on a version prior to Mojave (i.e High Sierra)?

Sorry, I am playing on Linux so can not `confirm' - but from the requirements Sierra 10.12 is minimum (so 10.11 may not work - and if so the gamer is to blame) but recommended is 10.14.
Thus if you want to use it on 10.12-10.14 and do have a real problem you should get your money back.

But of cause if someone can clarify that would be more precise ... so I hope this helps nonetheless.