Was it proven that the oil blew the engine? Most likely not. The engine may have blown due to other issues which is what usually happenes. People almost always think it is the oil's fault that the engine blew because the last thing they did was change the oil or went to a different brand oil.
Most of the time when an engine blows it is usually due to oil starvation, pump broke and or oil not circulating or part failures. I read a report some where that said and engine failure has never happened due the engine oil itself, it has always been something else. Not knowing the whole story about his failure and weather or not the oil was analyzed to see if the oil was still good or not at the time of the failure and weather or not the oil was used per AMSOIL's directions. I can only speculate why it blew. It could have been possible the engine had high mileage when he converted it to AMSOIL and the damage had already been there, this has happen before too. Everyone wants to blame the oil.
I have used AMSOIL for over 30 years and have never had any engine failure and have put over 200,000 miles on one vehicle that used nothing but AMSOIL. So your friend's decision to stop using and selling AMSOIL was most likely not made on a sound reason. I guess he would have stop using Castrol if that was the oil he had been using too Huh.
And by the way did you that a lot of Nascar teams use AMSOIL and yes they use a lighter oil to qualify (a 0W-20 or 5W-20 or lighter) and then use a 20W-50 racing oil to race for up to 500 miles and then the engine is torn down for analysis. But those are Race Engines not a passenger vehicle engine.
It would also be nice if you would not type with just capital letters. That is considered yelling and is hard to read. Just saying