LBR20 Firmware Manual Update --> is internet required to complete?

I updated LBR20 to 2.6.5.32 today and thought I'd bricked it...

Can someone who knows confirm whether the manual firmware install requires an internet connection to complete?  

I did a manual install from a file on my computer over a wired connection precisely because my cellular connection is unreliable.  After waiting more than 1 hour on the firmware update admin page, I finally gave up and logged out.  Obri acted like a brick and afterwards and I could not connect to the admin panel.  Not a happy experience.  I finally hauled Orbi outside to give it one more shot with the best possible bandwidth.  Then I was able to access the admin panel and was rewarded with a success message on the update. (Whew, not a brick after all.)

My guess is that Orbi can't finish the manual install without an internet connection.  If this is correct, that's not a good thing because cellular bandwidth can't be relied upon in rural areas.  I'd like to know so I can make certain to do any future upgrades in the middle of the night when the bandwidth is better.