Well, it can be confusing, because you can use the content tree to navigate the site in the main frame to page A (and page A will be highlighted in the tree) and then you can use the site to navigate to page B.

At this point, with page B showing in the main frame, page A is still highlighted in the content tree. So if you would start editing the page, you *could* be mistaken that you are editing page A if you look at the content tree, since page A is still highlighted.

In some tabs of the page, you can't see what page you are chaning, so you can make this mistake:

Hey, page A (highlighted) should have template X, not template Y. And then you change it, but you find out that you were actually changing page B...