I am pretty sure, with a known history, that the Bros R would strive nonetheless to deal with any major problem. They do have a superlative approach to customer care and I know it matters to them.
I cannot tho help but think of an extreme example here. Let's say someone bought a LNIB R9 and then punished the heck out of it - I mean like countless 1,000's of rounds!! While I know Eric's #1 has done extreme duty who is to say that a second owner might not disregard all recommendations re cleaning, lube, general maintainance and then have a problem due to this negligence.
It would be hard to then see total guarantee holding good for an abused pre-owned gun. I make an extreme example of course. I daresay - bottom line - if a gun that had been abused was returned other than from original owner, AND showed signs of severe abuse, I'd be on the Bros R side with regard to not having to make all repairs!!
Case by case basis this would have to be.