I also checked the code of com_content of Joomla and it looks like the column settings will be applied for Intro Articles only. I guess you're not setting to show Intro Articles so the columns setting doesn't work:
![](https://www.joomlart.com/forums/assets/files/2024-05-02/1714625319-89577-screenshot-2024-05-02-at-114654-am.png)
You can set the Leading Articles to 1 or 0 and increase number of Intro Articles, it will show correctly then.