Confusing instructions when to use resistors, Doorbell 3.

I'm planning to replace my old mechanical doorbell with a mechanical chime with a Video Doorbell 3 and keep the mechanical chime. In the manual, it says that you have to install a 25 Ohm, 50 Watt resistor if you hardwire the Doorbell 3 to a transformer. On the other hand, at Ring Help it says this in 'Important Information on Upgrading From Ring Video Doorbell 2 to Ring Video Doorbell 3': You should also remove any existing resistors when upgrading. **Resistors are not needed when hardwiring a Ring Video Doorbell 3.** The questions: 1. Am I right that you only need a resistor for the Doorbell 3 (and Doorbell 2) if there is no chime, only a transformer? 2. Why then should you remove any existing resistors when upgrading from a Doorbell 2 to Doorbell 3? Many thanks, Tom.