I'm really not sure that SG2 has proven itself yet. It just seems an extra barrier for promising younger referees to get promoted. How long were the likes of Atkinson, Marriner, M Oliver, Webb and Clattenburg on the Football League for before being promoted to PL and how long would they be now?
I don't think the system works if you're just having 1 or maybe 2 promoted to SG2 each year. It just creates a blockage. If necessary, the weakest 3 or so of SG2 should be removed from the list at the end of each season.
Like Gillett, Madden should certainly have gone to at least SG2 initially but presumably there wasn't a space. He now has to do at least a year just to get to that level and then at least another year to get to SG1. And that's presuming he doesn't fail a fitness test due to catching Covid during a pandemic and find he has to do another season at that level automatically.