The rocker arms only need a small volume of oil to lubricate them, but it MUST be there. The restrictors are there to prevent robbing the lower end of the engine of the necessary oil flow- - - - -if necessary, sacrificing the rockers to assure enough lubrication to the bottom end. That's a throwback to the "oil distributor" on the old spray-oiler engines, 216, early 235, etc. that restricted oil flow to the head until there was at least 15 PSI at the main bearings and oil spray tubes in the oil pan. From 1953 with the first full pressure 235s to the last of the series in 1963, there were several variations of the rocker lubricating system.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!