I have had this perpendicularity call out explained to me as follows: "The reason for the call out is really meant for construction of the die to stamp and pierce the part". It basically means that they want it pierced normal to surface (this is for sheet metal parts only) and not on some angle to the surface.

And, one the MMC call out, I have had quite a few engineers refuse to allow the bonus tolerance. Most, I think it is because they don't understand it. Certified or not, they just will not allow use to use it. We are not a stamping plant, but a construction source, we build the dies, they run them. The other possible reason is that they want to hold us to a tighter tolerance than they can use so that when they get it in house, it will look even better than what we showed.