I can tell you why I have not done the banana grooves on my shafts yet.
Because (for whatever reason) PRW uses two bushings of which the total width is less than the total width of the rocker body there is a gap between the two bushings and that’s where the adjusters and the oil hole at the top of the rocker get its oil.
If they used a full width bushing like RAU does then I’d groove them.
I suppose PRW does it that way because it’s cheaper. You give up some bearing area but so far I haven’t had that be an issue.
Yet.