2016 3'' front / 2'' rear level question

I was looking at a kit on Amazon that seems pretty straight forward for install. Blocks in the rear and the spacers on top of the strut in the front. I did see a video on youtube during an install job about changing the position of the differential. I never heard about this when I've installed similar kits on my GMs and other Tundra videos dont mention it. Is this something I should look into further?

 

If you are 4wd, they are referring to a differential drop kit. You will need a carrier bearing drop kit as well. On a side note, most of us don't like spacer kits, and you don't want to off road with one either.