Apple hasn't even warned us about the firmware issue. There is no indication whatsoever that if you install this through the mac app store, your firmware will be updated!
In absence of such warning it is prudent to proceed with caution.
If you would rather install it without the firmware update you can use the direct links method in the thread https://forums.macrumors.com/threads/1830603/
In absence of such warning it is prudent to proceed with caution.
If you would rather install it without the firmware update you can use the direct links method in the thread https://forums.macrumors.com/threads/1830603/