Massive torque applied from very long levers (the branches high overhead) onto a second class lever with a very short distance to the fulcrum, installed into an area of compromised strength (probably).
Even if the wood retains all its structural integrity at the time of installation, the very act of drilling the holes will increase the probability of decay. Cables mounted higher in the tree have all the same decay & fatigue considerations, but they are holding the split tree from a position of mechanical advantage, so they under mere fractions of the same extremes of pressure and force as a brace mounted much lower in the tree.
I can see how some splits would be much better served by a brace rod than cables, particularly for younger and smaller injuries. I had never considered the gain of eliminating friction at the split, so you have improved my appreciation of bracing.
Quite frankly, I have never installed a brace rod, nor have I ever encountered an installation. Even cabling is not a terribly popular option around here. For most of my customers, big shade trees are considered more a liability to remove than a valuable feature to save. So by the time they need fixing, I usually get a call to provide an instant and permanent cure for a split trunk.
