To be honest, I wasn't doubting that it was said. It actually would have been good strategy. If Sam convinced Fro to knife Richard, Richard would be a guarantee to NOT give Fro the vote in the finals. The only problem would be if Sam trusted Frofiles to eliminate SCM in the event that Fro won the final immunity.
It's a shame to see Sam go down due to Fro's underhanded tactics. Honestly, I don't think anybody in this game could have beaten Sam if he made it to the finals. His gameplay was admirable all the way through. The judges would have had to award this to him.