I hardly see that this meets the "exceptional circumstances" criterion from what I can see.
613 A person must not start or attempt to start a horse in a Race or trial (including a jump-out, or test for certification purposes with a horse):
...
(c) in plates having a sharp flange or sharp projection on the ground-bearing surface, or which are excessively worn or otherwise faulty or defective; or
(d) unless fully shod with approved plates in accordance with the plating provisions of the approved gear list determined and published by NZTR in accordance with Rule 609, provided that in exceptional circumstances a Stipendiary Steward may permit a horse to run unshod or partly shod.
There is nothing in the stipes report to the effect of that permission being considered or granted, nor on what grounds.