How does two independent pieces give a better alignment than aligning to the bar you lap with?
It shows you if the rings are aligned or not. When the centers don’t meet exactly there is a reason and lapping is not always the solution. It’s only an indicator of something wrong.
It could be out of spec rings, rail, drill and tap holes in the receiver off, etc.
it’s up to the owner to determine what is causing the issue.
I’m in the fan club of PEPR scope mounting because they are line bored as a unit. Never found one off yet.