You’ll see it better when you get your WE, but I think either way will work. Take a look at this photo…
(from this page Does the angle change…)
… in particular the angle change in the first example where it starts at 26.2, goes down to 25, then back up to 26. The pivot doesn’t really “see” horizontal or vertical, just the relationship to the pivot. If you’re sharpening a straight edge, the angle doesn’t change.
If you mount it like you suggest (which I’m picturing like an inverted V?), you should see the same thing… so I guess what I don’t know without having one in hand is which way would be easier to setup and duplicate as needed, and hit the angle you desire.