Stainless, Bushed PRW Rocker Arms

Rat Bastid said

Because the bolts are necked down. I’ve been running studs for almost 40 years and never had an issue.

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Take a stud and slip it into any newer aluminum head and see how tight they are. Also you can never be sure the stud is in the center of the hole to leave the oil feed hole side open. The taper on the bolts center the bolt for oil feed. The studs are straight cut and have no taper in the shank to center them.
I too never did this and been doing theses engines since the 70's. After building several high dollar engines and taking my engine to HTA machine (Very knowledgeable engine builder) My son and I learned some tricks on many different engines. There are many other tricks we learned from him. Like side bolt mains he installed. RB's use 3/8 bolts and B engines use 5/16 studs. Unlike many know it alls on this site we learn and use methods that make sense. Sometime you have to think with your "dipstick" Jimmy