I'd imagine it is down to the number of recharge cycles. A phone tends to go through an entire recharge cycle every day to two, whereas I'd imagine a Tesla wouldn't go through it's entire range as often.
If you check the interpolated cycle life at the source, the oldest Teslas have gone through <800 full discharge cycles, so only ~3 years of a phones life. However the discharge decreases nonlinearly over time so the Teslas have lost <10% of capacity while a phone loses >30%.