How style.css and functions.php can be in sub directory?

Hi All,
Sage 9 has style.css and functions.php in sub directory. In my understanding, WP only check them in the theme’s root directory. I wonder how style.css and functions.php can be in subdirectory?
Could anyone give me what makes it possible, and what I need to see ? I’m learning modern php, does it relate to it?

Thank you in advance.

I wrote a little on that here: "/resources" appended to sage theme name in wp cli The short version is that WordPress will look one level deep for those files, so Sage uses some filter magic to adjust directory structure.

If you need to those files in the root directory for some reason, there’s some discussion on that on Github: https://github.com/roots/sage-installer/issues/3

Interesting. WP looks one level deep for those files. Thank you.