what happens with the market and stock volatility when the market closes?

Hi all, my friends and I are doing a project for university and we got stuck.

We read on investopedia that when the stock market is closed, there is more volatility in the stock since there are less investors and there is a bigger ask spread. https://www.investopedia.com/ask/answers/05/saleafterhours.asp

But what happens with the market volatility? does that also decrease?

I found this article online: https://www.thecoldwire.com/why-does-the-stock-market-close/

But I am not sure if this source is trustworthy… They give 'reduction of volatility' as an argument for closing the market. It is nowhere stated what 'volatility' they mean; market or stock? I can imagine that maybe the market volatility reduces since less trades are happening, but I have no clue what is true now…

Can anyone help us out?