A 3T -ben nem a szokvanyos nagyobb kapacitasu akku van az elodhoz kepest hanem a voltot emeltek 4.4-re:
OnePlus themselves have confirmed that indeed the voltage is higher, but this goes paired with a battery that is more energy dense.
Therefor they were able to keep the physical size the same, but the chemistry change together with the voltage change allows for a denser energy capacity.
The effect on lifespan won't be as bad as originally estimated, but people are still concerned about the higher voltage no matter the battery's chemistry.