Picture #1 shows an area that is factory machining. Earlier slides did not have this area beveled if my memory is any good. Pic #2 doesn't show up for some reason. The trigger bar ears make marks on the bottom of the slide as can the slide stop arm as the slide drags over it after the last round is removed and the follower presses it up against the bottom of the left side of the slide. So, don't let the hardened pin at the catch notch peen the stop are to a sharp point that well chew on the slide. This goes for any similar set up whether aluminum or zinc. 1917
Above is a picture of an older slide and one without the bevel. I haven't looked at it closely but the only reason for the bevel that I can imagine without looking closely is that it helps the slide in this area slip over something when mounting. What is under it when mounting the slide....? I don't ever remember reading of any wear issues at this spot or mounting hang ups. What you see on the above slide is typical damage to the disconnect ramps under the slide that hit the trigger bar ears. When I slant my ears rearward this swaging of the metal is essentially eliminated. If you look carefully at the left, bottom of the slide you will see where the slide hold open arm drags a bit which removes the finish.