In strict answer to your question. I have had an octopus hook break on me one time in 20+ years of salmon/steelhead fishing. I have never straighten one and I have never straightened or broke a siwash hook. I am convinced it was just a defective hook. It was on a pre-tied, store-bought mooching rig, tied up with 15 lb. test leader.

That was the last store-bought leader I ever used and I have never had any such trouble since that time.