Yet how long after the hardware was absolutely capable of matching iOS for responsiveness in the current UI, did it take for Android to prioritize and achieve that goal and how long did it then take manufacturers to update their implementations? And to what extent has it filtered down to the bulk of cheap devices?

I don't think the (sane) argument is that Android can't match. Or that the hardware to match is unavailable/expensive. I think there's a valid point about Android having different priorities that often see it ignoring this area and the manufacturers of cheap devices generally just not caring to try. [1]

So inasmuch as iOS6-class performance was in reach of even the 'don't really care' class of Android manufacturers, iOS7 does present a higher bar (that they are likely to continue not really caring about), meaning tens-to-hundreds of millions of devices that don't (regardless of whether they could) match on visuals. Until the inexorable march of performance-per-watt brings them brute force solutions.

[1] Is Google even going to think it's worth the resources to chase blur effects at the expense of other features? And if they don't, would Samsung? And as the maker of its own 'cheaper' devices, would Samsung filter that higher-end look to its cheaper devices out of the gate? Or retain it as a differentiator to push people into buying new Galaxy kit, instead of the lower-end devices?