Why are there so many places in dutch unis? specifically, numerus fixus programmes?

Numerus fixus is for courses that are competitive but why are there 600 spots? That seems like an insane amount to me. Unis in my country have 30-100 spots depending on the course. In the netherlands is there like a natural selection system? i.e. rigorous course where a large number of students don't meet the criteria to pass first-year and get kicked out? Or is this number of students "normal" for dutch unis?
(I had this question when looking at the psychology courses for both university of amsterdam and university of groningen)