With LeafSpy, at least on my 2020 SL Plus, the charge gauge is correct past 50% and up but once the charge level gets below 50%, then the two start to diverge by over 10% until it reaches the "bottom" which at 0%, LeafSpy still shows enough power to drive another 30 miles. For technical people, yeah it would be nice if the gauge would add that extra +30 miles but I think as the battery sizes get bigger, all of us EV drivers are playing a game of dick waving (sorry ladies, don't know what term to combo that with) about who's number is bigger for remaining range. When I fully charge my EV, it shows 252 miles of range. Maybe it would be cool if it said 282 miles? Well I know it won't do 282 miles on the interstate doing 70 MPH but also it will do that range if I am driving slow enough to average 5 miles / kWH, so as has been repeated many times here, a real world test is just a set of variables tested and the results. My real world driving is much different than everyone else. I run tires inflated over 36 PSI recommended, I know how to minimize AC/Heat use, etc. We all learn the tricks to maximize range well past what the EPA test with.
2020 Leaf SL Plus - (Manufacture Date March 2020)
2013 Leaf SV (8 faithful years of service before trade in at 75,679 miles)