Do you still have the car? I think if you open the frunk and remove the 2 side covers (one left one right, very easy don't think you need tools) If the car is fitted with heat pump option I think you will see 2 coolant bottles one either side with green or pink coolant in them.I am confused about whether my I3 had a heat pump or not (2019 120Ah UK). When I switch the car off I get the option to start auxiliary cabin heating and it works, but when I query the car with the bimmer.works decoder it does not list it as having a heat pump (4T9). Does it have a heat pump or not ?
I might be wrong on this, I have a 19MY car with heat pump so I can look if you want to compare.