I think one problem could be that under some circumstances you get a scrum if you fail to catch properly, and under others you don't. I wonder if all coaches will apply the rules accurately.
My observation from last season was that nobody obeyed the instruction that the nearest players should form the front row. This time, with hooking required, I doubt if any coach will follow that. I suspect only a few players will be trained to hook. While I can see the desire to avoid early specialisation, particularly since the kids are still growing and may well change shape and hence position over the next 5-10 years, it seems unrealistic to expect everybody to learn to hook. You don't really learn the position until you play it regularly, and they can't all do that. Moreover the skill is not a transferable one like tackling, kicking, catching, and passing.