I use OrCAD environment for designing PCBs but I've never thought about what is the purpose of a Drill Symbol in padstack creator. The diameter is set in the Drill bookmark and other parameters like antipads or thermal pads in Design Layers. I can see it in the layout file. What is that used for?
They're used to create a drill chart, which some PCB manufacturers use to double-check things like the match-up of the CNC drill files and the Gerbers.
I seldom-to-never send it with the Gerbers and drill file. In my experience, not much goes wrong on that account and I doubt they bother looking at it. From this site: