From my opinion, RPRF request does not 100% guarantee upcoming PPR. I am saying this because of my friend who has a criminal record back in his hometown got RPRF request after his AOR. A couple of weeks after he paid RPRF, his criminal record check started to be under review and he has been stuck in that stage for a long time now - he was requested for some additional documents related to PCC issue. However, if the person has a clean criminal record, yes, it should be definitely good sign for upcoming PPR.