Do you have a reference for that? The variance of most traits will increase as the variance and volatility of the environment increases. My guess is that the variance in stature in countries like Holland and Sweden has actually decreased significantly over the last 100 years. Military recruitment records would be the place to start looking.

But I honestly do not know the answer. Perhaps I should ask an LLM. But this might be a goid place to start instead.

https://ourworldindata.org/human-height