Mine was a little different, not sure if the original post has a typo. As mentioned before the halogen units have as single fog (RHS) and Reverse (LHS) so you need to run 2x additional cables above the headlong to connect both sides.
LH Light
1. Grey/Black - Side light
2. Connect to RH Pin 5 (Additional Cable)
3. Black/White - Indicator
4. Brown - Earth
5. Green/Black - Reverse
6. Black/Red - Brake
RH Light
1. Black/Red - Brake
2. Connect to LH Pin 5 (Additional Cable)
3. Brown - Earth
4. Black/Green - Indicator
5. Grey/White - Fog
6. Grey/Red - Side Light
Having just done the additional wiring, I too had to do it this way. I done it the other way first and it was incorrect. 2019 highline kombi so possibly different because of the age difference?
Having two reverse lights is such a treat. Currently using Auxito brand LED lamps and they work a treat.
My advice to anyone planning on doing the same would be to buy the correct pin tool for a few quid. The Allen key approach works fine but definitely mangles the pins slightly.
Thanks for all the thread info.