The problem with putting un-rehydrated ADY in dough is that the amount of time it takes to activate the yeast is variable. So is the distribution of yeast grains through the dough (they're not likely to be uniformly distributed), as is the fraction of the yeast that will actually activate. (Something like 10% of ADY by volume is dead, but lots depends on storage and handling conditions).
If you're making bread at home, that's not a big deal: you can wait more or less time. for a commercial operation, it's a problem. (There are encapsulated yeast products used in frozen doughs; I wopnder if they're adaptable to fresh, delayed fermentation doughs.)