They didn't follow their logic far enough to see that it's conclusion was that Microsoft's designers are complete idiots who aren't following due process. Not anl totally impossible scenario, but it is sufficiently unlikely that it should cause someone to pause and re-examine their assumptions.
In reality, near the top of Microsoft's design considerations would be written:
*Phone must last around a day in order to be competive with rivals and avoid negative reviews in the press.*
And from that follows:
*Extra screen increases power draw. Therefore a larger battery will be specified.*