The comment on the Bren website that the 1600 ECU is organized like the S1000RR sheds some light on the question. In that ECU BMW employs something they call Reduction Pre-Control. It's a control table that limits the amount of throttle applied, regardless of rider demand, based upon the traction that it thinks is available at various lean angles and gear selected. It's designed to smooth the transitions in and out of traction control. For example, it "knows" that in the first few gears, and at high lean angle, that large throttle openings will overwhelm the expected traction of the rear tire - so it won't deliver a full throttle opening in those cases. Otherwise, the actual traction control would be activated much more often and seem more intrusive.
The guys that have this whole system well understood are the racers that have worked with BMW and Bosch to provide their own tailored tuning. The best explanation I've seen on the subject is a fairly long thread on the S1000RR forum and can be found here:
It's a fascinating read by someone who clearly understands the ECU and a great way to spend your day while your family is out doing Black friday.
Thanks for posting. Sounds much more logical and informed than the rampant speculation and ego swordfighting that has been occurring in this thread.