You get to use both ends : including the one to remove boy scouts from horses' hooves, and I only get to use the pointy end!
The thing I said about "messing about", goes double. If the butt-end was truly important there wouldn't be a plethora of funky styles.
What is the expression? Better to be thought a fool than to open one's mouth and remove all doubt. No thanks, you apparently already know all you will ever know about yari and how they were actually used.