ok, i had a bloody good look this morning out of curiosity.
my 09 handbook also has a loose leaf amendment saying stickies are reqd.
you need to take off the wheel arch light cover to access the back if the HID bulb lens & i 'think' there is a lever, as indicated by the handbook, however the area is near as dammit inaccessible due to location & bodywork.
i draw the conclusion there is a switch to flip the lights, & these lights (or at least the internal gubbins) are common to other models which are more accessible & can be flipped, but in practice, it is not possible / practical / wort the effort on the e89 due to the position of bodywork, hence the change to say use beam benders.
thats my take on it.