Essentially I think it's more to reduce the odds on favs then to make it easier to win the Vicbred bonus for 4yo and older horses.
I am wondering though if it will have the unexpected consequence of 4yo C0's leaving the pool of racehorses sooner once they have won one race and their Vicbred bonus. Can't claim or drop back from a C1 to a C0 and they'll now be contending with the winning 3yos twice in the already stronger C1 class and I'm tipping many of these 3yos won't start much longer in C1 class then they do in the C0s. Perhaps the Vicbred bonus needs to be awarded in part for the C0 win and C1 win to keep these horses in the racing pool with prospect of obtaining a bonus until they attain C2 class, and drop back, mares and junior driver concessions apply.