how to prevent a theme from using templates of a sub themes (placed inside the parent theme dir)?

Question

my folder structure looks something like this:

📂 themes
└─ 📂 foo
   ├─ 📂 bar
   │  ├─ 📂 templates
   │  │  └─ 📄 node.html.twig
   │  └─ 📄 bar.info.yml
   ├─ 📂 templates
   │  └─ 📄 page.html.twig
   ├─ 📄 foo.info.yml
   └─ 📄 foo.libraries.yml

now I run a multisite. one site is using the foo theme and the other uses bar.

The site using the foo theme also invokes the template /theme/foo/var/templates/node.html.twig

1. Why is that so?
2. I thought the foo theme only invokes templates inside its own templates folder? I expected this to be the point of the templates folder. Is that assumption wrong?
3. can I prevent this behavior without moving the subtheme somewhere else?

Answer 1

Themes are not allowed to be placed inside one another, as oppose to modules. Even though it works, there are undesired side effects.

Answer 2

This directory structure is shows one single theme called foo. The sub-directory bar has no meaning at all for Drupal, it is below /themes/fooand as such part of foo.

Your node file has to go into /themes/bar/templates/OPTIONAL/SUBDIR/DOES/NOT/MATTER/node.html.twig

Every theme, even subthemes, has to go in it's own /theme-directory. Please red read the docs for sub-themes.