Originally Posted by Mad Cook
Browning doesn't really seal the meat's surfaces but it adds to the flavour due to the maillard effect.
So it is worth the bother of doing it.
Unfortunately, despite the subject of McGee's book, cooking isn't a science. If it was then every time you cooked a dish it would turn out exactly the same. You can do the same thing with the same ingredients 10 times and get a slightly different result each time. That's part of the pleasure and the interest of cooking.
McGee explains the science of why things happen. For example, why the Maillard reaction happens and the temps at which it happens, or why brining does what it does. Beyond that, how a cook implements a recipe with minor variations in how they execute these steps causes variations.