If you click the 'more info' button in the description, you can see he specifically states this
So I would contact him first - but I would also query the fact that he is incorrectly saying these are made by Harman Becker - they are NOT. They are made by Magneti Marelli as all the RT* units were. I think he is getting his MyWay (WIPNAV) and eMyWay (WIPNAV+) units mixed up:THIS STEREO IS NOT COM[PATIBLE WITH REVERSE CAMERA
WE CAN SUPPLY UNITS WITH REVERSE CAMERA ACTIVATION FOR £350
It may be a genuine mistake, so I would ask him to get his listing info correct first of all and confirm that you need an RT6 or WIPNAV+ unit with Rear Camera Support.MANUFACTURED BY HARMAN BECKER
MODEL BE6426
RENG2