Very interesting article.
However, according to SpeedTV, this part is not entirely accurate:
The suspension layout is supposed to remain stock, but BMW caught a break from the Automobile Club de l’Ouest (ACO)—it sets the Le Mans (and ALMS) rules— because its strut front and multilink rear setup would have been uncompetitive against rivals that have control-arm suspensions. Hence the M3 GT has specially fabricated control arms at all four corners.
According to SpeedTV, the cars that ran at Le Mans were somewhat different from the ALMS cars. In particular, they had the front strut/rear multilink suspension instead of the ALMS double-wishbone suspension. When asked whether this was true, M. Theissen dodged the question.