Interesting. I think most of us just assume our rig is centered, though it might not be perfect. None of our hulls are perfect to begin with.
Ultimately, I would depend on my dealer for this kind of advice, but I'll offer an observation:
If this is the older Aka bar style, then the geometry of the bearing plate is fixed in place by the position of the factory installed brass inserts. You have to go with that. All you can do is tilt the receiver cup until it squares better with the bearing plate and lock it down. I would do this with the mast in place.
Yes - The mast "should" be basically centered port to starboard, but I suspect that it is supposed to tilt back somewhat, as it does on most boats. You'll notice that the bearing plate leans back at an angle relative to the opening for mast receiver. This makes sense for sailing upwind with the sheets pulling the mast back hard.
This is a TI mast for illustration...