I don't think it's snake oil, but.... From the description:
1) The device doesn't work on Normal mode. Only Eco mode. Hmmm....
2) The device appears to add B-mode for models that don't have it. But since all US models have it...
3) Increase max power from 80 kW to 83 kW. Well the factory came with a 85 kW electric motor (2015 and 2016), so I interpret this as slightly increasing the max current flow to the motor during max throttle application. Since the 2017+ already came with a 100 kW electric motor to partially compensate for increased battery weight, we already know that this slight bump in current will have barely any improvement in acceleration.
4) More stable power delivery. This is a city car, not a freeway car or a track car. I prefer the unstable, but immediate rush of immediate torque that the car delivers at lower speeds. But that's just me.