There has been a lot of debate as to what exactly we should do when a user changes the "context root" section of that page. We've never really come up with an answer. Our options included changing the context root in their descriptor file, or, if they don't have a descriptor, creating a new descriptor file and setting the context root there. This was pretty unpopular. Other options were changing the war deployment name, which also seemed non-intuitive for a user.
So basically, ti's a property that WTP has put there, but that we haven't figured out how to use in a way that works for us. So we mostly ignore it (sadly).