In J.D. Trues' book about running trains on the White Pass he directly states the rotaries had flangers and somewhat insuates some locomotives did too. Like Bret said I'm not sure if the 19 had pilot flangers either. I think someone who would know that reads this board is Jeff Chittick. Jeff are you out there? SV Cartoad might know as well.
As for the tire wear the tough work of rotary service is mostly to blame as Mike said. However I've heard the 19's running gear wasn't as badly worn as the 20's when they returned from Alaska. The 20 ran for a year longer than the 19 and this might have something to do with it. Also according to Jasper Sullivan who worked on the WP he said that towards the end of steam they were losing a lot of the old steam heads who knew what they were doing. This explains the "well worn" condition of some things.
This is good stuff about the White Pass, keep it coming.