Actually the gap is because it is easier/cheaper to machine a mass of separate parts and have them fit each other regardless as the tolerances as so loose.
Machining rings the way we do is much less cost effective, but you get a precisely mated "pair" of rings that require NO lapping and because they are made as a set in 1 piece there is only a .010 gap between the ring halves.
The big downside I see to any ring with a big gap is that it is easily possible to crush the scope tube by over tightening the ring screws, with out rings it is virtually impossible to crush a tube.
FWIW to replace the scope tube on a NF scope figuring in shipping to and from Idaho is just under $800.00. We just got the estimate of repair back on a scope that the tube was crushed using NF rings.