The normal sense is based on 360 distance, which does not change when you change aspect ratio. The scoped sensitivity is matched using MDV 0% or something, which is a FOV based match, and the FOV changes a lot when you go from 4:3 to 16:9. PS, the correct way of doing custom aspect ratio is to enter your native resolution, then select the appropriate AR from the dropdown.
The calculator needs to know both the real aspect ratio of the monitor and the custom aspect ratio used.