Holding very rarely has anything to do with the flying training system and a lot more to do with changing requirements on the frontline. It's easy to blame PTC/22 Gp/mfts but the reality is that holding of various lengths has always and will always be a thing if you change the demand on the frontline after or before people have been recruited and trained to fill those slots. Some folks get lucky and zip through with zero holds, others spend some time cooling their heels. The key of a long hold is to get a proper job and learn something about the real world from it.