Scraping off the flash is quite a different thing from removing enough material from the hub to fix an imbalance problem. I fix out of balance hubs with medium CA and kicker. I even went so far with a big 20 inch prop as to pound out a thin sheet of lead and glue pieces of it on to get the hub balanced right. The effort may not matter much in the grand scheme of things, but I'm able to get my props balanced near perfect, and it doesn't take long. There may be a benefit in the long term durability of my planes, so I do it.