Some Themes not showing posts older than 2019?

I’m trying to migrate my site ( away from using a hacked version of the xmin theme to using another theme, but I’ve noticed other themes I’ve tried (paperCSS and notepadium) don’t show any posts older than 2019 on the front page, while still rendering those pages (they show up in category lists and when I go to the pages themselves).
Why do some themes behave like this?

Hello. I maintain the paper css theme. As seen in the demo, the homepage shows posts of various years.