Lithium-ion battery charging/cycling
When charged to a maximum "full" state lithium-ion batteries are driven to 4.2V per cell. Near that voltage there begins a plating out of lithium at the anode which can oxidize and vent with some danger
of fire and/or explosion, given sufficient material, time, and temperature.
When discharged to 1.25 Volts per cell there is a danger
of copper dendrite formation between the anode and cathode, again giving rise to potential instability when recharged...not safe.
When cycled between levels about 3.95 Volts per cell and 1.3 Volts per cell one gains reliability
yet does not optimize the number of likely cycles for greatest life. Somewhere between the approximate "safe" cycling over an 80% dynamic range (versus the not-so-safe potential 100% rating) and a high cycle life of a 60% dynamic range is the optimum cost per cycle over life dynamic range.
I believe that the article misinterpreted such specifications to state incorectly that the battery is only charged to a 60% state-of-charge instead of correctly stating that a 60% dynamic range as compared to a possible 100% dynamic range. With a 60% dynamic range usage the battery is charged to around an 80% or up to 90% state-of-charge depending upon the "safe" reserve allowed at the lower end to accommodate self-discharge for sufficiently long periods without dendrite formation.