No, it is not damaging to your battery, but it is also not that simple. All cells coming from the manufacturer are rated to certain standards. For example a cell might be rated for 500 cycles. This would be under the assumption that you are charging each cell to 4.2V (Volts) and discharging to 2.8V. If the cells go lower than 2.8V it can start causing significant damage to the cell, but the battery management system (BMS) in the device prevents this from happening. So as long as your BMS is working properly, draining your battery all the way is not damaging the battery according to the manufacturers rating.
Here is the caveat to all of that. If you want to extend the cycle life of your battery as much as possible, it is healthier to never drain or charge the battery all the way. When the cells are at an extreme (all the way full or all the way empty) they will degrade faster - but not faster than the manufacturer expects them to. More on charging to 100% here.