Makes sense. The longer the batteries are in service, the more we will be seeing of this.
For me, the December 26th (I think) firmware update that de-restricted previously restricted vehicles speeds, ended up restricting my MX.
My 2016 MS was capped at 94 kW rate 2 months after taking delivery, halfway through my first road trip. So as you can imagine, not too much use on my Model S yet at that point It was "de-restricted" to a point on that Dec 26 update, now I can hit 115kW.
On the flip side, Christmas Day, December 25th, 2020, I was able to charge at 144kW. Dec 26th firmware update installed, on December 27th, max rate capped at 112kW, and drops like a rock. I can only see the rates for a minute or two then drops to around 70's-ish. Regardless of temps.
Battery fully warmed in each case at 113*F or warmer (I have CAN BUS Access).
Further, Tesla is fudging BMS data, including charge cycles, and a lot more starting with firmware 10.x. This isn't the right place to get into all the nitty gritty details, but it is quite sad =-( Just one example, total battery cycles. I was at 1000 cycles on my Model S (I've been recording BMS data every 1000 miles since new at 100% SOC, now just under 150,000 miles, MX is at 118,000 Miles). I was at 1000 cycles one day, check next day and was at 950 charge cycles, day after that, 1010 charge cycles. Charge cycles isn't something that varies that much like total battery capacity.