Android Design – Can a Fragment Know Other Fragments?

I think I have found contradictory design guidance within the Google Android documentation on fragmentation.

The first statement below advises each fragment be unaware of other fragments and always communicate only to the activity and let the activity decides what needs to be done.

Creating event callbacks to the activity

In some cases, you might need a fragment to share events with the
activity. A good way to do that is to define a callback interface
inside the fragment and require that the host activity implement it.
When the activity receives a callback through the interface, it can
share the information with other fragments in the layout as necessary.

For example, if a news application has two fragments in an
activity—one to show a list of articles (fragment A) and another to
display an article (fragment B)—then fragment A must tell the activity
when a list item is selected so that it can tell fragment B to display
the article. In this case, the OnArticleSelectedListener interface is
declared inside fragment A:

But a second statement later on the same page, a list fragment directly instantiates detail fragment.

   if (mDualPane) {
        // We can display everything in-place with fragments, so update
        // the list to highlight the selected item and show the data.
        getListView().setItemChecked(index, true);

        // Check what fragment is currently shown, replace if needed.
        DetailsFragment details = (DetailsFragment)
                getFragmentManager().findFragmentById(R.id.details);
        if (details == null || details.getShownIndex() != index) {
            // Make new fragment to show this selection.
            details = DetailsFragment.newInstance(index);

            // Execute a transaction, replacing any existing fragment
            // with this one inside the frame.
            FragmentTransaction ft = getFragmentManager().beginTransaction();
            if (index == 0) {
                ft.replace(R.id.details, details);
            } else {
                ft.replace(R.id.a_item, details);
            }
            ft.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_FADE);
            ft.commit();

So my questions:

Are these contradicting each other?
Should this be left to Activity?

I feel confused, so any clarification is appreciated.