Motorhome 440's... factory seconds?

I was talking with a mechanic at work who is a big mopar fan. He was telling me something I had never heard... motor home 440s are typically factory seconds. He said if they screwed up and had to repour the block and other things like that it found it's way to a motor home. Is this common knowledge that I've just missed? Or just heresy?

Cheers!
Drake