I don't understand the comment about exceeding the design voltage. You wouldn't expect an overcharge to result in higher battery voltage, unless they're talking about the charging voltage being higher than spec.
Overcharging LiOn cells is manifested by continuing to run too much current through them after the charging current has dropped to a low level, like 3 percent of the cell's rated current capacity. But the voltage, at that point in the charging cycle, has been at a constant level for most of the charging period. It quickly ramps up in the initial charging period, then settles as the reverse current through the battery drops steadily.
Perhaps they meant exceeding the charging voltage, during the charging cycle?
Overcharging a battery is not the same as overfilling a gasoline tank, if you are equating voltage with gallons of gasoline.