Gary Illyes from Google explained when he thinks it makes sense to use a hierarchical versus flat structure for your website. In short, he said larger sites might benefit from a hierarchical structure if they want to encourage Google to crawl sections of the site faster.
Gary said in the Google SEO office-hours from December 2023 at the 1:35 mark, "for a large site it's likely better to have a hierarchical structure." Why is that? He explained, "that will allow you to do funky stuff on just one section and will also allow search engines to potentially treat different sections differently." He said when it "especially when it comes to crawling" this is something that you may want to consider.
"For example, having news section for newsy content and archives for old content would allow search engines to crawl news faster than the other directory. If you put everything in one directory that's not really possible," he said.
Here is the video embed when he said this:
This is not the first time he said this, he said it in Septemeber 2022.
Forum discussion at X.
