I think the perpendicular illustration was to try to clarify a question raised on irregular OB. Example would be the OB is a right angle and the disc lands off center on the corner in bounds.
It's not perpendicular from that line as a whole, but perpendicular from any one point on that line.
I made a terrible graphic to illustrate this-
Further, there are odd loopholes in taking your one meter in a "corner", as it were. Like this-
I believe that this was the case on Hole #17 at Swope Gold at this years KCWO. Where in that corner, taking 1 meter of relief would bring a player closer to the other part of OB. So instead of taking 1 meter from where the disc went out (deep in the corner), a player would take 1 meter of relief from any OB, which would ultimately bring that player more like 2-3 meters from where they initially went OB.