It looks like about half of the countries in that little map are off of their natural time zone by at least as much as Spain. Including basically all of the former Soviet Union, except the Ukraine and Baltics. And Iceland. And, well, France, which mostly overlaps Spain time-zone-wise.
Indeed, it seems like an incomplete explanation at the very least.
France largely overlaps Spain in terms of [latitude] longitude, is in the same time zone, shares some of the traditions cited in the article (long lunch break, midddle-of-the-morning and middle-of-the-afternoon coffee breaks, dinner at 8pm), and has one of the highest productivities in the world, in line with the US, Japan or the UK (above if you count it per hour worked).
So maybe they should look for an explanation somewhere else
