That figure will be maximum instantaneous power output allowed from the battery as limited by the BMS.171.6kW max power? That's 230bhp! No wonder it's quick
That includes ancillary loads including heater, A/C, DC-DC inverter that charges the 12v battery and (effectively) runs 12v accessories like power steering etc...
Also keep in mind that this figure is power before the motor and drive inverter so doesn't include losses in both drive inverter and motor/gearbox. So you won't be getting 171kW at the wheel even if heater etc were turned off.
As a comparison the motor in my Ion is rated at 47kW at the wheel, but the BMS reports maximum possible power output from the battery as 55kW - the "missing" 8kW allows for heater/AC load and drive inverter/motor inefficiencies. The car is able to put out full rated power at the wheel even when the heater is on full consuming 5kW.
The point of this maximum power output figure (and there is also a maximum power input figure) as managed by the BMS is so that when necessary the BMS can lower the cap on the maximum power output/input for example due to state of charge or temperature, and these set limits that the drive inverter aren't allowed to exceed.