It appears they don't. From the responses, the sloppy rich camp attribute the difference to original manufacturering differences rather than break in.
From what I've seen, FBD will never believe. He's convinced himself it's a myth. He's been shown direct quotes from manufacturers, statements from engine experts, and real life examples where sloppy rich break in did result in lost performance. His responses are just back pedaling and refusal to accept what others have already discovered.