Im not sure that the little brass inserts are actully restrictors?
If you watch the quanity of oil pumped up around the follower and spills out onto the little platform with the brass insert, you will see that is not much, my opinion is the brass insert is to direct the oil to a more accurite position to drip onto the cam.
Just my theory.
Do what you want.
The little "pin hole" that is in the UK head certainly restricts oil drain back to the cam lobe.
You can't even get much water to drip through that hole.
The north american CVH engines have never had an issue with early cam wear problems.
My cvh engine had 270,000 km on the same camshaft - the lobes and lifter bottoms show almost no wear. One has to assume the extra volume of oil getting on the cam lobes helps??
Just trying to help. I guess I will keep my big mouth shut!