Phones these days take good care of their own batteries, 100% doesn't actually mean 100%, same with 0% since both are extremely bad for Li-ion batteries.
Interesting product, thanks for mentioning it, you can limit how much you charge your phone battery the same way as a Tesla.
Just use it like normal and budget in a ~$100 battery swap every 3 years or so.
Also by looking at metrics of my wife phone you are basically even after about 1.5y - 2y (gets to 80%), so you loose battery life first but after that time you are net positive.
If you plan sticking to your phone for longer time, then it's good investment.