I don't know if it is in any industry standard, but my justification is that if you are using a folded radius dimension and have holes located normal to that radius, it would be good to visually indicate their orientaion relative to the radius center. This would be especially true if the hole centerlines were offset from the radius center.
In my example the centerlines are model entities, and I used two identically oriented views to show them in the drawing, connecting the centerlines with lines on the face of the drawing.
"Good to know you got shoes to wear when you find the floor." - [small]Robert Hunter[/small]