If you are talking about clearance from the rocker body to the spring/retainer, any variation is probably due the rocker being a cast part and the rocker shaft hole doesn't go perfectly into the same spot for each and every one. So there is wall thickness variation that could cause the gap to vary. The PRW rockers I have do this. Some clear and some don't. It is obvious that the castings are hand ground/polished on the outside and not identical from part to part. I would not expect to see this variation on a set of extruded rockers and would be very cautious if they did.
