Engine shop I worked in years ago fitted undersized cam bearings to every engine regardless of what it was and the engine assembly guy reemed them to suit.
I have heard of that, but that is done to verify alignment more than to adjust clearance although you could do that too.
My point was that I have never heard of anyone saying that cam bearings are a natural restrictor. A bearing is a bearing and they leak oil under pressure. It is very common to restrict flow to the cam bearings to force more oil where it is needed at the crank and rod bearings. That guy was dismissing that. I am ok if someone doesn't agree, but come back to the thread and tell us why so maybe we can all learn something.