Around Germany and Greece there were other countries. They went by names like frugal four and PIIGS. They forced "austerity" and stricter working hours onto indebted countries to save their own banks.
The colours on this map show well that northern "productivity" is not about working hours, but about other topics that did not get addressed. Among these topics are also tax heavens (think the Netherlands) and money laundering (think Austria's special relationship with Russia).
So it was nothing more than poor political leadership without vision.
Both this and the OP seem kinda confused, honestly.
The working hours argument was never an argument in the first place, at least at the level of government policy. This chart was used to dispell some myths among the population, but it wasn't particularly new information for anybody making policy even at the time.
If anything, a frequent clarification in the impacted countries was that this shows a productivity issue in some of the Southern countries, where more hours and less output is an issue. And yes, the weight of retail and service industry jobs has an impact on that. Also, to my knowledge, this IS about actual worked hours, not contracted hours. These numbers don't match contracted hours per country, and were bandied about to explain why excess overtime damages productivity, not the other way around.
None of this had much to do with austerity, beyond promoting or dispelling some stereotypes. Austerity was about investment and public spending and was demonstrably, patently some bullshit. Dogmatic German-style (and Dutch and British, don't think I've forgotten) anti-spending policy proved itself counterproductive, useless and imprevious to facts, as the US kept cranking up investment, particularly under Democratic administrations, and outpacing European growth.
Which is not to say that Southern economies didn't need reforms for productivity and increasing employment. But those reforms weren't about cutting spending or public investment, beyond plugging the hole the housing and investment crisis left behind.
Thanks for putting the effort to detailing this.