I did read on "GM Authority" that export models were available with 6.2 for 2016.
I have been told by several people "In The Know" that the reason we can't get them here in the US is because of the Federal Fuel Mileage mandate. Since 5.3's get better mileage than 6.2's GM tries to put as many 5.3's on the road as possible.
Back in the 60's when my Dad was selling Chevy's...you could check off certain RPO options and force an order through. That's how you got a 2 door Biscayne Sedan with a bench seat and a 425 HP/427 4 speed !!
I talked to an Army Sargent stationed in Germany that bought a Tahoe with a 6.2 there and had it shipped back to the US with out any issues...just the $$$$ to buy it a boat ride !!
Not that simple these days with the Fed in every body's business.