That's a really good point, it's actually a constraint of the architecture of the web. This framework is based on our own research of the best way to reliably measure page performance is across page loads.

Boomerang itself is actually a generic beaconing framework so you can use it to beacon anything but it also has a lot of bootstrap code as well for performance testing.

Phil has done some great documentation on how to do beaconing right to go with the framework and you should expect more of that.