The OEM hitch lacks a longitudinal member to resist the torque a WD hitch places on the receiver. I looked at how a trailer shop in Canada adds a reinforcement and I agree with BMW's recommendation that WD is to be avoided unless you strengthen the receiver attachment, and add a fore/aft reinforcement bar to resist twist. Unless you don't tow often and you are using light duty WD bars I would avoid WD.

I just sold my high end enclosed trailer because it needed WD (tongue weight near 1300lbs when loaded up), and bought a bare bones all aluminum ATC 20' to keep weight low enough to avoid the need for WD (tongue weight about 200lbs empty).