We just recently moved from a 2016 T8 to a 2020 T8 (lease was up on the '16) and I have found that when putting the transmission in Brake Mode "B" that the vehicle behaves inconsistent. Both my wife and I drove our '16 extensively and know how it should feel when in "B" mode.
With the new 2020 in "B" mode, at times, there is no difference between "B" and "D". You can literally shift between the 2 modes and there is absolutely no change in behaviour. Typically speaking you should feel the vehicle slow down in "B" mode as it uses the kinetic energy to charge the battery. Living at the top of a hill, when in "B" mode we can drive 2- 3 km to get to the bottom and still have a full charge. We have found, at times, this doesn't happen and although in "B" the car behaves as though it is in "D". When we get to the bottom of the hill part of the battery is used (ie 1 or 2 km).
I know the braking system is changed in the 2020 from our old 2016. I feel like it is a bug in the system. Of course I will take it in to have it looked at, but curious if anyone else with a 2020 T8 has experienced this behaviour?