As a bit of a battery expert for the past 20 years, I can tell you without a doubt that keeping Lithium chemistry between 3.78~3.9v per cell is chem neutral and will increase longevity; what this equates to in the BMS as a % is undefined. Whenever voltage moves outside that range more oxidation happens which is degrading your battery.
An Asus tablet 100% equated to 4.12v and 0% = 3.55v.
My RC charger 90%=4v.
% really depends on the BMS and some manufactures like to ensure no puffing and go conservative, others don't.
But really I think Europe with all it's regulations should mandate user replaceable batteries, bcos you're going to lose ~50% in <5 years with conservative use, and the max you can expect is <10 years.
I think Sony claim 500 charges, 15hrs music = 312 days if you're lucky.
My Dell XPS charges from 50-70%, I believe it best to always keep your device 30-70% for best battery longevity.
100% battery long time is worst.
0% for long 2nd worst.