4.05V is 94% of 4.2V. Does that translate to having 94% capacity longer. For a total capacity over time greater than maxing to 100% with an 20% falloff?
You are assuming that a battery is full at 4.2V and empty at 0V. In practice a Lithium Ion battery is empty at 3V. You are also assuming the relationship between capacity and voltage is linear - it is not.