They don't care about that. They don't care if it's within 10px of the right location, or whether it's one DOM element or multiple, or how it's structured. They

They don't care about that. They don't care if it's within 10px of the right location, or whether it's one DOM element or multiple, or how it's structured. They care it looks right, and that certain things look identical between builds. The size and position of the BBC logo, for example, must be in exactly the same position. Also, this means it can be verified by a non-technical person. All you need to do is verify that the differences are either 1) wanted or 2) irrelevant, and this is an extremely simple and robust way of achieving that.