I think the Windows version uses DirectX for graphics. The macOS version uses either OpenGL or Metal. I always write my software with OpenGL for cross compatibility and if that's what they used for the Mac version, then it should be pretty easy to port it over. I'm hoping the code base between both operating systems are already shared meaning there's code that looks like this:
#ifdef MAC
doMacThing()
#elseif WINDOWS
doWindowsThing()
#endif
However, if they used the Metal API on macOS, they'd have to port graphics code including shader code over to OpenGL (which is what they should be using anyway...)