Rear Diff no drain Plug?

[BMW-North]

I got around to changing the rear diff fluid on this e83 today and it's the first BMW I worked on that did not have two plugs in the rear diff. I couldn't find a second so I referred to TIS and sure enough they have an optional diff (188L) that only has one plug?

Anyone come across this - how did you drain the fluid? this is BMW asinine.

Here's a pic of the TIS saying "No drain plug" - doesn't bother to say exactly how to drain it either.