Rex,
The purpose of my earlier, almost off-hand calculation was to disabuse the notion that the 10%/4000 lb load could possibly apply to the shank capacity. It seems to have done that. I knew the diameter was slightly small so as to include something of a stress concentration factor, however an actual factor would likely be even more severe. Even with your unfounded speculation as to the yield strength, the result confirms that the 4000 doesn’t apply.
I suspect Aurora builds their stuff to perform adequately for their envisioned application. Given the 40,000 lb rating, it appears the material is probably in the 105,000-110,000 psi yield range, a fairly common mid-level fastener material. But there are many ways to get there that may or may not include some hidden pit-falls. Perhaps when you confirm the actual shank chemistry, heat treat, tensile properties, hardness, Charpy values, geometrical concentration factors, residual stress, and hydrogen embrittlement/stress corrosion cracking propensity of the steel in a marine environment, a more accurate assessment could be made.