I got bike rack prep on my Roadster and that was two things: a second towing eye for the rack to fit into, plus a swing-down trailer wiring socket behind the bumper to work the lights on a bike rack.
Since the F56 comes as standard with two towing eyes, I'm guessing the bike rack prep is just the wiring socket behind the bumper.
On the R56/7/8/9, the bike rack still needs a control unit added to the rear wiring of the car to make the wiring socket live, and do things like disabling rear PDC when the rack is fitted. Again, I'm guessing the same system will be used for the F56, where the control unit comes with the bike rack and the fairly high cost of the bike rack includes fitting the control unit into the rear wiring of the car.
None of this would apply in the USA, where it doesn't seem normal to fit extra lights on a bike rack. For them, every F56 must have bike rack prep just by having the second towing eye.