To be honest If Sony can increase clockspeeds without an appreciably negative impact on yields or power consumption it would be stupid not to as they are leaving available performance untapped.
Right, so the only sane assumption is that the performance figures they released to developers are what they thought they could get with acceptable yield and thermals. Trying to get a 25% increase in performance, like to 5TF from 4.2TF, would generally require nearly double the power consumption and corresponding generated heat. It just doesn't seem plausible.
If they have tweaked the design in any way from the leaked specs I'll be very curious to see where. Only people very familiar to the hardware know where the bottlenecks are, and therefore what would make a real difference.