This is no mistake.. This is Yahoo!’s definition of being complete. Apparently for Yahoo! 99% is enough to consider something complete. Where I work, 99% is actually better than most people will ever attain, but that still isn’t enough from Yahoo! (maybe that’s why their stock is lagging).
When I was using Yahoo! back before their IM client had file transfer, I was impressed that chatting could be handled in a non-server-client LAN environment. Now I know that Yahoo! is not going to impress me any more than that. As another example, doesn’t it seem clear to everyone that you can’t chat while being idle?