After 11 years, a change in SOC behavior?

All,

After having the HV battery and HV ECU in my 2002 replaced at 100k on the dot, I've noticed that SOC stays at a near rock-steady 75% with only a very occasional drop to 50% (maybe 5% of the time, if that), whereas for the life of the car to the best that I can recall up to this general point in time, displayed charge fluctuated between 50% and 75 on a 50/50 basis.

I can almost accept that with the the replacement of a couple of major hybrid components, there could be changes in the electrical/electronic characteristics of the hybrid system that would account for the change in SOC behavior. Except that I first noticed the change about 6 weeks prior to the battery failing.

But here's the kicker: Within weeks of my battery failure, Linda's 2002 started showing the identical change in SOC levels (note that her car only has about 62k). We took her car to the dealer for a scan. No codes were found, no battery leakage, the cells were reported to be A-okay and the car was otherwise given a clean bill of health.

I realize that the Energy Monitor is not a great source of accurate or detailed data on the condition and performance of the hybrid system and granted, both cars at the moment drive just like they're new, with no power or performance issues whatsoever. But after 11 years (and pretty much to the month, mind you), seeing this change in the SOC behavior is puzzling to me... it doesn't quite seem to add up.