I don't know about that one, jjtjr. Cutting a bevelled end will give you a larger opening than just leaving it round. If anything, you'll collect more rainwater. But if drip-pan elblows have not been omitted by the designer or contractor, then it shouldn't matter.
I was always under the impression that the larger opening of the bevelled end was to minimize the velocity of the discharging steam (or whatever fluid is being handled).
If nothing else, it's the mark of a proper fitting job - that attention was paid to detail. It's like walking into a boiler room. At least 99% of the time, your first impression tells the tale. If it's a nice, clean plant, and looks like it's been taken care of properly, it likely is, in all respects. If it looks like a dirty junk-hole, it likely is, again, in all respects.