No but gudies on YouTube to do it without needing root
Never need to root to flash new images onto a Nexus
Just don't flash userdata.img & everything will be fine.
Don't even need to worry about that, download the OTA zip file and sideload it with the stock recovery.
Isn't that what he just said?
I thought Matteysan refered to the factory image and Rusty was saying it's even easier to flash the OTA (which wouldn't wipe data anyway).
I have always downloaded the factory image & not flashed userdata 
Well, they're publicly accessible on Google's servers, as that's how the phones get them.