2017 GMC/Chevy DEF tank!

Just yesterday I was sitting at a light in my Prius work truck looking at the new OTR tractor next to me. Both fuel tanks and DEF tank was right out there in the same position as the new GM pickup truck's DEF tank. It looks odd on the pickup but I don't see it as being any more of a problem.
Back in the '90s, folks said diesel pickup trucks weren't as good for off road as gas powered pickups due to the weight up front. What changed?