This would tend to back up a theory that I have.
I bought my 2016 R/T used in October 2017. Going in, I was aware of concerns from others about Full readings and "gallons per fill-up". Usually, when filling, I would get a needle just below full and it would drop a bit fairly quick. I also would get the "low fuel" light and rarely be able to put more than 15-16 gallon in on fill-up. I have drove well over 100 miles on the light a couple of times before putting in just about 17 gallons in a 20.5 gallon tank.
Here is what I do now. I still get the low-fuel light and can only put 16-16.5 gallons in. I can live with that. I also slow the input nozzle down considerably for the first few gallons. It seems that my fuel gauge will read fuller, and for a longer period, if I take more time to fill. It also seems to read better if I fill before the tank reads under 1/8 - 1/4. I put almost as much in at this point as if I let it drop to the red line (with-in a gallon). My thought is there is an air bubble in the tank that needs to be slowly worked out. Can I prove it? No, that would require crawling under the vehicle and studying the shape and layout of the tank to see if that is possible. I don't find the issue to be of any concern anymore. My gauge works fine following this practice, my mileage is good, and I know that I have spare fuel in the tank if needed.
If you are so inclined, and curious, try it. It would be interesting to hear feed back from others.