The Dutch had an unusually high level of urbanization. Until the 20th century, urbanization was correlated with worse nutrition.

They took account of differences in income for modern Dutch people but not historically I think. I don't know how poor the average Dutch person was relative to other European countries back then that might explain them being small at that time either. The change since then is so extreme relative to other societies that to account for it with an explanation that is just as applicable to all other European societies just doesn't seem plausible to me. Some sort of health or nutrition explanation peculiar to Holland and perhaps to do with childhood intervention (e.g. effectiveness of vaccination programmes, childhood or pregnant mother care, smoking rates etc) seems more likely.