His main reasoning for suggesting this is not the die shot itself but because he's comparing the number of blocks and extracting the size he THINKS it should be based on Tahiti/Pitcarn, which is fine if it was the same architecture and offered similar performance and had the same feature set.
Unfortunately, while Pitcarn/Tahiti are the same architecture, Hawaii is not, it increased performance significantly beyond the die size increase(40% faster, 24% larger.....). Ignoring die space required for things like powertune 2, true audio, that tmus/shaders/rops/just about everything could have changed enough to account for the supposed difference in die size is rather silly. He's decided "it's just the same architecture so double the rops of Pitcarn means double the space, X % more shaders vs pitcarn means x % more space taken up.... then added it up and decided it should be 5% smaller.
It won't be to do with power. More shaders + lower clocks give the same performance, but lower clocks mean lower voltage, lower voltage = the most important thing in terms of power usage. It's probably not true, and if it was and if they aren't yielding well enough now, they likely won't be before 20nm comes along and any more time spent trying to respin it is a complete waste.
Nvidia release Titan at £800, then 780gtx at £600, then when AMD spanks it they drop it drastically to £300-400, thus everyone who paid £600 initially could and really should have been paying £400. Titan should never have been sold for more than £600(well less really but meh).
AMD came out and put the 290x at £420, the 290 at £300......... if the did release a ridiculously low yield 290xtx part it would be £500 and wouldn't actually change the pricing on the lower parts. Hence you didn't get screwed and wouldn't be.
In this case 290 buyers paid £300 at launch, pay £300 now, and will pay £300 even if a 290xtx uber edition comes out.
Bringing out a new part if/when yields improve or they can just get enough together for a non awful launch(if they only get 20 working dies per wafer, you couldn't even launch with 5k for a VERY long time) doesn't matter IF it doesn't screw existing buyers completely. AMD both have offered great value AND helped Nvidia buyers out by increasing the value of their buys. Unless AMD brought out this most likely fictional fully enabled part and AMD dropped the 290 down to £200, the 290x to £300 and priced it at £400, that would be screwing customers in the same way Nvidia likes to, but they didn't bring one out at a time months apart with insane pricing screwing their customers. The very first launch was everything they had available and at extremely competitive pricing.