Need to reboot to upgrade to Safari 5.0.1?

Didn’t Microsoft get ordered to decouple their browser (IE) from their OS (Windows)? So, I got this Software upgrade dialog on my iMac and I see that it asks me to reboot to upgrade to Safari 5.0.1! Why should the OS need a reboot to upgrade a browser? I don’t like that at all. Yes, these days browsers do a lot of things and they are themselves like mini OSes. But, they should be designed like any other app on the native OS. Shouldn’t require a reboot of the main OS.