It's surprising to see Iceland, New Zealand and Australia that high on the list. They don't have a reputation for being workaholic nations.
I could understand if self-employed people were included, as temporary staffing shortages are often covered by business owners.
I also wonder what the hours for office workers are like. I'm sure that most public sector employees work fairly regular hours.
Perhaps some people are temporary or "zero-hour" contractors with more than one gig?
Every office job I have worked has been 38 hours with no overtime save for a handful of exceptions in 8 years of tech work.
Mining on the other hand can have consecutive 12 hour shifts be the norm, and I am sure that it gets worse than that.
We have some fairly strict award rates/employment regulations that govern things like that, but mining seems to be perhaps one of a few exceptions.