Version (6.1.18030.17371, 30-01-18) here.
In the attached file, with “Snap to occluded objects” enabled in Modeling Aids, draw a line between the two points (Point osnap). No problem.
Now, undo, disable snapping to occluded objects and try again. Point snap will no longer snap to the point on the surface from the side facing the camera. If you turn the view over, it will snap from the “underside”. The point on the surface has been placed with the “OnSurface” osnap…
SnapToSurfacePoint.3dm (58.6 KB)