This has gotten discussed on the Bob list and other spots over the many years, and it's fairly well proven.
I've been using a coarse wood rasp to remove material from the rear of some of my problematic brake pads in a similar fashion, and have seen reduced squealing.
I will add that I've had more troubles with KoolStop red brake pads, which seem to get stickier in humid conditions (i.e. summer here in the midwest). Older pads that have had a chance to harden are less sticky and less prone to squealing. Still, I've been surprised that the red Koolstop pads in the Campy Record brakes on my Olmo can squeal enough on a soggy summer day that it will cause the quick release lever to gradually open up! Some additional work with the rasp has improved the behavior, although I'm not sure that it is completely cured.
Steve in Peoria