I have come to the conclusion....
The crank rotates 360 deg.
If the timing mark is pointing at 12:00 it is in the correct location. No need to check tdc
The camshaft rotates 360 deg.
If the timing mark is pointing to 6 o'clock it is in the correct location.
No need to check anything else.
I have seen engines that reference 12:00 for both but that's seems to be the exception.
If you think I'm wrong, look at the lobes on the cam to the gear mark, the lobes will be in the same position as long as the dot is in the same location. Same for the crank.
That's why the FSMs don't need to tell you how to index other then align the dots.