Again, I state that the shank is by itself by the far the strongest part of the assembly. Consider the pin which is .31 sq in. that's just 15 percent of the shank area. It too is subject to constant dynamic loading. Consider the receiver which is about 1.75 sq in or 40% of the shank area. It's constantly subject to dynamic loading and torsional loading also. Do you really think that the shank, even if made of mild steel will be the first item to fail?
Is your pin made of chrome moly? Do you think that truck manufacturers use chrome moly in their receivers?
I think not.