Recursive delete function doesn't delete folders with curly brackets in the name

Question

I'm using the following function to delete all files and subfolders from a folder, before removing the folder itself:

public function deleteDownload($dir): void
{
    foreach(glob($dir . '/{,.}[!.,!..]*',GLOB_MARK|GLOB_BRACE) as $file) {

        if(is_dir($file)) {
            $this->deleteDownload($file);
        }
        else {
            unlink($file);
        }
    }
    rmdir($dir);
}

This works great, until the program stumbles upon a directory with braces in the name, e.g: {test}. When this happens, the program throws an exception saying that the directory is not empty, which is correct as it contains files that should have been deleted:

ErrorException rmdir(/Users/xx/xx/xx/xx/xx/storage/app/c544946e914f/test//{test}/): Directory not empty

When I rename the filename from {test} to test everything works as expected.

Can someone explain to me why this happens and how to fix this?