NSFileProviderExtension folders not listed when searched in the Files app

Hello,

I'm working on a File Provider Extension, and I've discovered something unusual. When you search the Files app, it lists files from any extension (iCloud, on my phone, DropBox, Google Drive, etc.) but folders only come from Apple extensions.

I wonder how can I have my folders listed in the search results...

By the way, I'm using

public.folder

If someone can help me on this, thanks in advance.

(Using Swift 5, Xcode 10.2, iOS 12.2)