Yup. I noticed that on my 2016. When I first posted about that several years ago a lot of people thought I was smoking something. I’m on a Dodge forum as well and a member their happened to actually work at the Chevy plant where the Colorados were put together. He checked into it and an engineer there told him the Silverados and Colorados used the same basic tank form. For the Colorado they stuff the fuel overflow sensor deeper into the tank so fast fill cuts off around 20-21 gallons. But if you slow fill you can stuff another 5-6 gallons in it. Here the photo proof. The reason given was Chevy was afraid a 700 mile range mid size truck would cut into Silverados sales which are more profitable

 

Now that is really interesting. I will have to give that a try doing slow fill on my next long hwy. trip..
Luck

 

It is tougher to top of the Capless Fuel Tanks
But, you have been able to get numbers like an extra 5 gallons in many Fuel Tanks in the past

 

I have alway been concerned about getting fuel in the evap system and call it full when the pump clicks the first time. But I seldom run the pump at full throttle either.
Luck

 

It was explained to me by many that the EVAP Flapper that opens in the Filler Neck Opens into the Filler Neck.
And It can not open against fluid
Depending on the Fuel Tank Filler Neck can be in Front, Top, Side or Rear of the Tank
Park on an Incline with a Half Tank or So... The Filler Neck could actually be Full of Fuel

My 2005 Tahoe Z71 had the Flapper Stick Open.(It would just Hang Up too long)
Dealership was able to spray it with some Lube and it worked fine after that.
If that did not work.. They would of had to replace the Filler Neck and the Flapper

I used to until the Capless System on my 2017 Z71 would fill up and the Fill Up the Fuel Tank until the Flapper at the top of the Filler neck was closing in gasoline.
Only EVAP issue from 1988 to 2016 was the Flapper sticking on the 2005 Tahoe Z71

 

An old guy years ago told me that if you fill the tank as fast possible - a large portion for the tank is vapors/foam. Fill it slow and it's more gas. I fill at the slowest setting possible and consistently get 18-22 gallons with around 1/4 tank already in the tank.