I've fished alongside thos who have used the floating crust when I have used the bread roll rig and have witnessed some blank sessions whilst this rig produced.
My feelings surrounding this rig and the 'Y' factor is based on the way it is rolled, trapping in all the attractants nice and tight, then caged by the line again keeping in all those lovely attractants. It hits the water and slowly but surely the attractants are released, they continue to release as the rig soaks up more water, the investigation process kicks in, the frenzy starts, the competition heats up the fish move in, they drop their guard, they ignore the hook, they ignore the line, the swirls hit hard, the take comes fast and wallop, you're away!
As where perhaps a floating crust releases all of its attractants in one hit and then just sits there remaining non-active. The bread roll rig is continuoulsy releasing attractants, smells, feeding signals way after you've cast out!