I'm a bit confused as to what your thesis is, but perhaps it's because I'm distracted by the fact that there seems to be a misunderstanding of what the data show.
FTA:
>The concept used is the total number of hours worked over the year divided by the average number of people in employment.
(emphasis mine)
My understanding is that the stereotypes are about "Germans" and "Greeks", which implies total populations (presumably defined by residency or nationality or something similar), but that data uses, as a denominator, only that portion of the population which is employed.
The inclusion of the population at large, or, more importantly, the population that could be employed, is discussed elsewhere in the thread (outside of the notion of stereotypes) as being a more useful indication of something like labor output (at least as compared with potential total output), especially when compared with GDP.