First, I am not speaking for Rohrbaugh in any way, just putting myself in a manufacturer's shoes...
Its one thing to feel some loyalty to a customer who put money in your pocket. Its another to deal with someone who bought the gun used from someone else and is becoming a problem. I think there is a distinction to be made.
I think we can all envision customers whose unreasonable demands might lead a company to need an "out" from a lifetime warranty.
Several gun companies with similar policies have repaired used guns for me. Others have never asked for proof I was the original owner. But, I always made my requests professionally and sent in guns that were well taken care of and in need of reasonable repairs.
I am sure there are people who buy worn out, used guns for a song and hope for a free factory refurbishing. I am also sure there are people who shoot loads that are too hot and want guns fixed as a result, etc.
I think that if you buy a used gun in decent condition made by any manufacturer and have a true manufacturing defect surface that would have been covered by the original warranty--chances are very good it will be covered.
On the other hand, if you are an unreasonable pain in the ***, you might find your manfacturer looking for a reason to deny your claim. Its human nature.