I heard this "Protestant work ethic" idea applied to European countries too (for instance to the Dutch, or more generally Northern vs Southern European countries).
Yet the standard working week in the Netherlands is just 38 hours (per Wikipedia), and in Germany it could be argued that the economically most successful states have a catholic majority (although this shifted after WW2, for instance from Saxony (protestant) to Bavaria (catholic)). I think the idea of "Protestant work ethic" is mostly bullshit these days, and it's more about worker's rights.
FWIW the 38 hours needs a lot of perspective. That average is mostly pulled down by individuals who feel pushed to work part time and individuals who are already making so much, taking an extra day off every week pays off more than getting most of the money taxed away and still being out of reach.
The above creates a dynamic where people will still work 40h to hit breakpoints, or will drop down as much as possible to stay at their current breakpoint (because working more isn't getting them there anyway). Doubly so because income tends to be a far bigger decider for things like housing and rent (highest expenses) than budgeting.
Because pretty much every Asian country was a rural wasteland in the 50s and 60s, and hard work and education is what got a lot of people out of that poverty. If you're white/only speak English, Chinese 40-60 year olds probably won't talk about this in front of you, but it's a widespread belief in China that Americans don't know what true poverty is like and are thus lazy.
That kind of makes sense, but not for Japan, which industrialised in the 19th century, so wasn't poor "a rural wasteland". It was war devastated post-WW2, but my understanding was that the working culture was there since industrialisation - which to be fair, was also the case in Europe until labour movements brought regulations at the cost of their blood. Maybe Japan just missed that train due to a combination of factors?
I want to say poverty as a one word one liner, but I'm really interested in a genuine explanataion.
However poverty and appearing to work hard to be at the top of an extremely competitive scramble out of poverty is my rough idea that isn't too hand-wavey in the direction of religion or culture.
Singapore has been high income since the 1980's and still has a very intense Asian work culture. The latest generation or two grew up in a very comfortable lifestyle, so any sense of "desperate poverty" is something their grandparents talk about. It even rare for Singaporeans to do much manual labor now, it's mostly done by foreign workers.
And other SE Asian countries (poorer than Singapore) have more of a reputation of "work shy" cultures. If you can work enough so you're not starving and have a house and beer to drink, why work harder?
So clearly the link between poverty and a "work hard" culture is pretty weak.
In one of Malcolm Gladwell's books this was explained as a by product of rice farming culture. Apparently in those climates rice grows all year round and every day you take off ends up hurting your bottom line, giving rise to hard work culture.
Yet the standard working week in the Netherlands is just 38 hours (per Wikipedia), and in Germany it could be argued that the economically most successful states have a catholic majority (although this shifted after WW2, for instance from Saxony (protestant) to Bavaria (catholic)). I think the idea of "Protestant work ethic" is mostly bullshit these days, and it's more about worker's rights.