Here are a couple of photos showing in photo 1 a not so good effort of finished undercut at the corner pocket. This one more so because it is supposed to be a steel block match table. I have seen much worse than this, but to point a few things out, the rubber at the top edge is too sharp and can cause the cloth to split if left sharp. Yes rubber can cut through cloth quicker if not sanded slightly at the cut edge. The undercut is convexed, it has been sanded but not at the back edge, where you can still see knife cut marks.
The second photo Below is of the correct way to undercut the corner angle, nice smooth lines no sharp rubber on the upper edge. Undercut is concaved to allow for the round edge of the ball to slightly tuck under the lower flat face as it enters into the pocket on impact to the undercut and no knife mark cutting in the undercut at all.
This work was carried out by Geoff large a Time served billiards fitter of GCL BILLIARDS , over the years the art of cutting and shapeing the rubber has not changed much , but the angle and undercutt has been changed many times to suit the modern play and the governing bodies , some fitters recutt the rubber to the old fashoned angles , if you want it done correctley to modern standards contact GCL BILLIARDS .