Presuming that the fights are made: If PBF loses to SSM that it doesn't mean that he would have automatically have lost to Manny. If Manny loses to Clottey that it doesn't mean that he would have automatically have lost to PBF
It depends how Floyd loses to Shane on how much I'd think Manny beats him. Even then, it obviously doesn't guarantee that Manny would have beaten Floyd just because Shane does. However Manny and Shane are just simmilar enough in style and aggressiveness that it would make me think that yes Manny would have beaten him too. Even then it's not something I would argue, but you can bet that it'd be enough for me to pick Manny over Floyd if they match up sometime after that. Now it's just the opposite if Clottey beats Manny. IMO that holds no bearing on a Manny-Mayweather fight because Clottey's and Floyd's styles are so completely different. I'd expect Clottey to win off of pressure, strength, and power. If Floyd beats Manny it'd be off of skills, defense, and intelligence.
I can agree there isn't such a thing as "automatic" in boxing. It's a dumb poll and I refuse to cast my vote.