I am surprised that the accelerometer needs any orientation at all. In fact, if there is some link between it and the compass, then I would think they need to be in sync as to what they use as a reference direction. But if the accelerometer and compass use two different standards for their calibration, then wouldn't they get confused? I am reminded of a joint Mars mission between NASA and Europe. It crashed when it got to Mars because NASA used imperial measurements and Europe used metric. The margin of error was small, but it was significant when carried out to many decimal places over a long distance.
So, anyone care to explain why true north is even an issue with the accelerometer?
As for the compass, magnetic north makes sense, but only because every place on earth has a different magnetic north. I have been told that if you move very far from where you last did your calibration, you should do it again, since the magnetic north bearing will change.
But that brings me to yet another question. Why is the compass orientation even important? After all, AFAIK, there isn't anything critical going on that requires a precise bearing in typical flying. For example, if you do a RTH, the bird only knows where it used to be in relation to where it is now. So it will fly back relative to its current position. So, if initially north was calibrated as west, everything would still be magnetically relative to how the compass was calibrated and it wouldn't get lost.