Thank you for your thoughtful reply. I admit, I've not learned enough about GIDs. It's very difficult to find an explanation of how they are calculated (or even what GID stands for).
I'm aware of the voltage drop, but that happens as watt hours are removed from the battery. Are you saying that volts times Amp hours doesn't equal watt hours? I don't think the voltage dropping while discharging means the watt hours were never there. It's just part of the calculation that shows the current watt hours, and drops as they do.
I also know all about loss of capacity over time/miles. My previous four Leafs taught me a lot. All batteries are not created equal! My first 2018 still had 40+ kW after 18k miles and constant fast charging for LYFT driving. My last 2018 came with a bad module in the HV battery. After 3 visits to the dealer, I finally convinced then that "If it charges and drives, you're good, no warranty issue" is not an acceptable response to a car that dies on the freeway while showing 75 mile range left!
They said they replaced the module, but the capacity dropped to 80%, and that module's voltages are whacko, so I'm pretty sure they somehow just cut the system's access to that module.
But as I was shopping for a good used SL Plus, I found that Leafspy pro showed around 54 kW at 100% for all five cars that I checked, regardless of year model or mileage. I checked a 2019 (40k mi), 3 2020's (18k-38k mi) And a 2021 (13k mi), and none of them showed more than 54.5 kW at 100%. But they show 62-64.5kw when calculated from the volts and amps. Hence my question about what is accurate, And, did they ever really have 62kW, because all range and economy indications point to the 55 kW being accurate, and I'm starting to think that's all the Plus models ever had.