I'm a bit confused as you're saying this article refutes your hypothesis, right?

I'll also offer up an example. The Polestar 2 (prior to 2024) has an advertised 78 kWh battery, but also clearly only 75 kWh available for use. That's about 96% right from the factory. So presumably it's doing what you're saying, but it's also not a secret. It's also a way to prevent regular 100% charges from happening, which have proven to accelerate degradation.

Their data fit on the extracted (supposedly real) data between 100k and 300k km suggests that you could drive around the planet 5 times while losing only a few percent of total battery capacity and I don't believe that raw cells behave that way regardless of recent improvements.