True, but there are still max. torque settings due to the physical size of the fastener.
eg. from the "Standard Torque Values table" at :http://electronicfilters.tpub.com/TM-10-4330-237-13P/css/TM-10-4330-237-13P_105.htm
even a 12.9 strength M-8 is only rated to 45NM, a 10.9 strength to 35NM, an 8.8 or 9.8 strength to 25NM and 4.8 strength to 13NM.
I just had another look at the nut and it appears to be marked 9.8 on the lower side so that ties up perfectly with the 25NM torque specified in the coupe engine manual.
So the 50NM from the guides is definitely wrong. I guess most people have just been tightening the nut by hand and not reaching much above 20-25NM , but I used a torque wrench and could feel the thread stretching before it hit the 50NM setting.
Hopefully they've made the stud a 10.9 and the nut has deformed first!