Will meat overcook in a boiling water pot?
Yes. 

Water boils at about 212F (100C) and meat is cooked from 140F to 160F. If you left the meat in there for a very long time it would eventually approach 212F and start to get tough.

The time that they give you is going to be the time it takes to ensure that the meat is safe to eat. Generally I like it to be closer to the rare side as it is more tender that way.