The page you linked looks correct on my system.
What I don’t understand is where you see “apple-system”. In a drop-down selection choice? If so, EXACTLY where do you see that? On the Customizer Typography menu? Somewhere on the Weaver Legacy Options Admin interface? On the editor? Do you see in the system debugger. What device/computer and browser are you using that shows this?
There is absolutely no where in Weaver Xtreme that “apple-system” is ever used or mentioned, so it is a puzzle how you would ever see that.