WST does burn cleaner than W-231. However, as a reloader for almost 50 years I am puzzled by the continued emphasis on the burning characteristics of powder rather than the end result - accuracy.
My favorite 45ACP accuracy load is 3.8 gr. HS-700X behind the 185 gr. LSWC for ca. 710 fps - a very mild and accurate load at 25 yards. It spits out grains of unburned powder grains but produces consistent velocity spreads of less than 10 fps. By current standards it would be considered a dirty burning powder but I love the end result.