You indicate the rear buttons will always trump Shutter button Af point selection, independent of order pressed, is this correct?
What about the AF Drive? Did it switch to the BB One Shot?
It seems correct from my testing - the exception would be if you use the (-) pass though setting so that it uses the same AF point that is currently selected.
Yes it switched to One Shot if your BB (OF-ON or *) was selected for One Shot - but you have to make sure you are fully holding down the BB button to keep this mode engaged.