Well 2 points:
1. it is also relative. Those cars back then that got 30 when the truck was getting 15 now get closer to 50.
and 2. it may have been the sales guy because I do not want to call your uncle a liar but no way do I believe 30mpg on a supercharged SRT. I am by no means a truck junkie but I honestly did not know and would have been shocked. I looked it up, and if he got the 3.6 engine with 2 wheel drive he is looking at 20/25, if it is the ecodiesel maybe a little more. But all they did was take an engine that should be in a chrylser 300 and put it in a truck, made the truck parts out of mainly aluminum so it is lighter but not as durable.
the only 2022 supercharged engine with 500+HP I could find was the 6.2L. This gets 10mpg city, 14 mpg highway so not much has changed bud. You also have to think they run these tests in ideal conditions with all stock options. I rarely know anyone that has a stock truck. At minimum they throw some bigger all terrain tires which will take some off your MPG as well.
Here is the link for reference:
https://www.stokeschrysler.com/ram-1500-gas-mileage/