Has anybody ever heard that a bad catalytic converter can either cause or contribute to engine failure?

What is your question?

My engine builder has had two new engines fail, one with 580miles, the other with 1860miles, and is warrantying the second engine but is telling me that my cats are bad and led to this second engine failure. I told them that I suspected that the first engine's bolts were overtorqued (cam seals and valve cover seals leaked from the start, at 580miles the rod bearings were so ground down that the oil filter was full of metal shavings, not to mention it never ran quite right. When the second engine failed, I suggested that they didn't flush out the oil cooler, or replace it, which led to the failure. After two weeks of inspection as to the cause, my mechanic is having me replace the oil cooler and the builder is saying the catalytic converters are bad and caused the failure. The car passed emissions three months ago, before the OE engine failure and all this nonsense. Having said all of that, I've had cats fail before to where they were so clogged the engine wouldn't run, but it caused no permenant engine damage. I've never heard of bad catalytic converters causing engine damage and I used to build race engines for a race car shop, have worked at other independent shops and I studied cars for three years in Auto VoTech classes during high school and received an AA from WyoTech. So I'm just curious if anybody has heard anything like this relating to the G35 specifically.