Correct, 50% of the original flow should technically be coming out of each of the exit barbs. However, if you were to restrict one exit barb with another waterblock and not restrict the other, you'd have something like 30% of the flow going through the second waterblock and 70% of the flow going through the unrestricted exit barb. Uneven back pressure on the waterblock and a lowered flow to the chipset block...not good.
Not sure how to make this work, unless you route your tubing farther away and then come back around to the chipset.