So I did some quick digging and it does seem that there overall work week in Netherlands is rather flexible. That said I did find this from Arbeidstijdenwet:

2 The employer organizes the work in such a way that the employee aged 18 years or older at most work performed during:

a. 12 hours per shift;

b. 60 hours a week, and

c. average 48 hours per week in each period of 16 consecutive weeks.

Legally the upper limit you can work in a week is 48 hours. But that’s the upper limit and not what is happening in practice. So I looked that up as well. For full-time employees I found that men average 38.4 hours and women average 35.0 hours. The average work week of 31.9 hours doesn’t mean Netherlands has 32 hour work weeks, it’s just skewed lower primarily by part time workers.