Upon further review, I think I’ve found the finger.

I’m bothered by two things, the boot choice, and the threat of the pink rock.

Here's what Maxx says:
Cochran does not like these odds. He seems to be playing a series of 3 day games, playing from one immunity to the next.

So Cochran flips allegedly because he’s worried about the odds of pink rock. Well, he has no need to worry, does he? If he’s “in” with Upolo, he knows where their vote is going, and Savaii has the idol to play. Upolo tells Cochran the vote is for Keith, they give the idol to Keith, and no worries about any rock. Further, Cochran not only buys himself 3 more days but another week, as the Pagonging has begun. He’s not a challenge threat, so he’s no longer in danger of being voted out as a challenge liability. He’s got friends and they trust him, since he gave the idol back. Why wouldn’t his tribe keep him around longer? The “flipping to avoid a pink rock and buy 3 more days” theory just doesn’t ring true.

Esp. when the target is Keith. That’s almost too obvious. If Ozzy wins immunity, naturally the target would be Keith, the next biggest challenge threat. If the vote was 7-5, then Upolo must have told Cochran the target would be Keith. Do they actually trust Cochran, someone who allegedly is playing both sides, and follow through on this obvious plan? If they think Ozzy is overacting, they must suspect that Savaii still has an idol, in which case they should be wary about it being played against them and the vote wouldn’t be 7-5.

I guess what it boils down to: either Upolo trusts Cochran or not. I find it hard to believe that they trust him enough to tell him they’re all going to vote for the obvious Keith without worrying about an idol bounce. If they don’t trust him, the vote wouldn’t be 7-5, it would be 6-5-1. In either case, I have trouble believing Cochran finds this is his best play, being a clear #7 in a 6-person alliance, someone who has no better shot than to be a F3 goat (if that).

This makes me suspect whether something (whether intentional or not) might be misleading about the info we’re being fed.