Engines are comparable to motors, not batteries. I would love to see any data you have on battery life. People lump all EVs together and make statements based on zero data. I don't do this with ICE vehicles or EVs.That study says nothing about these batteries lasting longer than ICE drivetrains. Battery charge retention is not the same as battery failure or reliability rates.
Battery charge retention compares more to engine compression retention, as this directly correlates to mileage one can do on either one charge or one tank of gas.
EVs are different and as a mass produced product are in their infancy. I happen to believe they will get better. And our car, a 2018 Tesla Model 3, is an amazing car and is different at the same time.