Yes, typically the generator is set to only be able to access 3/4 the tank. They say it is safety so you don't get stranded.
My current rig with 200 gallon fuel tank means I can still drive about 150 to 200 miles. If I can't find fuel in 15 to 20 miles I must be blind!
2012 Newmar King Aire w/ Roadmaster Falcon 2 Tow Bar
2020 Cherokee Trailhawk w/ Blue Ox Base Plate