It is also idicative of a ferrule put on before the shaft is final sized and the shaft moved then was cut down to final and finished. Seen this on some expensive customs that don't thread, and was disappointed when I saw it. Threaded ones you can tell, there is glue between the wood and the thinner side and then wood right up to the ferrule on the thicker side. Even a zero clearance threading will show a bit of glue on a thru ferrule at the end due to the angle of the thread and the faced off edge. A slip on fit ferrule will not show a glue line at all, if done right, but will show a thinner side if it wasn't kept straight through out the full process. That's why I put mine on at the end of finishing a shaft, not before.
Just my two cents,
Dave