Bull***t.
I can upgrade the firmware for the NIC and SCSI/SAS controllers, and their drivers, on my Windows systems without requiring a reboot.
It's pretty sad if OSX makes you reboot for an application library update.
It's always been the case. This isn't a critical component so hold it off then? I'm sure that strictly a restart isn't needed, all that needs to be done is restart various applications that use webkit rendering. A restart is just a way to make sure all webkit apps are restarted for the average user. You can always force quit the installer when it asks for your to restart.