I don't think there is a good case under 5.9.1.2, for turning blocks attached to the mast to be considered halyard 'deck blocks' that could be relocated. I'd put this in the category of "impossible to foresee" and "not within established practice" thus a measurers ruling. I'm unclear if this gizmo gets bolted to the mast as well as through the deck and if the tie rod shown is then attached back to the mast or elsewhere. There is the issue of whether the J/30 deck was designed for such loads. 22-28 years of experience has shown that, not withstanding cracks, the mast can.
