Apple could be getting specially binned 1.3 ghz chips, which would (somewhat) justify the price increase over the 1.2g ghz model, as it doesn't look like a standard chip.
The 5Y71 base clock is 1.2Ghz at a TDP of 4.5 W but can get to 1.4Ghz with the TDP at 6.0 Not sure how Apple got it at 1.3Ghz but thats what they claim.