There are many non-linearities:
resistance vs angle
angle vs height
tank width vs height
Presumably Mopar designers accounted for all when winding the fuel senders, but my guess is they made it much less sensitive near full. That seems typical for all cars, perhaps the purpose being that when the salesman says, "try if for the weekend", the gomer potential customer thinks, "great mileage, drove 300 miles and the needle still on 3/4". What really matters to me is how accurate "E" is. I don't care too much about "F" being perfect since I fill it until the pump clicks off.
In my Mopar dash clusters, I had to add parallel resistors across the dash gage input, plus adjust the gages a bit (have 2 factory screwdriver adjustments for zero and range, for experts only) so that the ebay Chinese sender read E and F right when bench-tested. Had to take one sender cover off and bend the wiper arm for more tension so it wasn't erratic. Also used an adjustable 5 VDC source so fuel and temp gages read about right (tested w/ resistors). Haven't tested in-car yet.
We still see idiots posting about their car mileage, using the tics on their dash gage. The only accurate way to measure mileage is the volume used from fill-up to fill-up which uses the calibrated fuel pump reading. Average multiple fill-ups to account for the pump not clicking off the same place. Don't trust your dash odometer until you calibrate it against highway mileage markers or GPS, and might need to calculate a windage factor to apply.