Both of my BMWs had linked brakes and they are amazing. Pull the front levers and the system decided how much front and rear you need. Use the rear lever and you only get rear brakes. This system (linked) only works with an IMU, in my opinion, early versions used line pressure and were a mess. You don't feel them working, just completely confident stops and a stable frame. Really no reason to use the rear pedal now, other than pivoting in tight spots. I think on the BMW GSA when you go to off-road pro mode the link is defeated.I don't know if the linked brakes can be shut off though unless they are electrically linked...
Time will soon tell.
Maybe you can shut off the linking, but I think Euro rules don't allow you to defeat ABS.