When I raised my seats in my 2017 Spider I also had a cable from the passenger seat with no sign of the connection to the car. As I am sure this was the first time the seat was out this was how it came from the factory.Did the passenger seat today, and guess: there was a cable coming out of the seat, but just hanging loose, not connected to anything. No connector on the ground to connect it to, strange. Forgot to try (will do so) what happens if a passenger is in the seat without wearing the seatbelt.
Apart from that: great to have both seats in a higher setting at the knees