Exactly, heck even customers with the 6.2l trucks wont run 91+ because they don't want to spend the extra money on the gas. Case in point, girl I work with has a GM truck with the 6.2l, she didn't even know the truck had it. I mentioned did the dealer tell her she had to run 91, she said nope. I pointed out the gas cover states 91 only on the 6.2l trucks, she still puts 87 in it because she doesn't want to spend the money.
I have never ran less than 91 in my truck, I even made sure to tell my dealer when they filled it up to not put anything less than 91 in it, when they tried to rebut it by saying it wont hurt I told them it is stated in the manual and on the gas door. They finally listened and put 91 in for me.