I think it runs under the assumption that it wont let the cap move away from the block. I have difficulty understanding what stops the "strap" from applying to much pressure to the cap. They are dissimilar materials and shapes so expansion and contraction will occur at separate rates. Further, the straps do nothing to address the concerns of cap walk if they are not connected like a girdle.
My biggest concern on a small block would be cap walk and splayed gear on a two bolt would be best as suggested earlier. In addition, the force trying hammer the crank out of the bottom of the block has more of an effect of closing the cap at the parting surface. This can be demonstrated by taking your caps and wailing on them with a ballpeen hammer on the center of the inside of the cap. Eventually, you end up with a closed or broken cap.