The WP core navigation-link block doesn't support current-ancestor feature which was available in the legacy menu system.
Previously we had the following classes available:
- current-menu-ancestor
- menu-item-has-children
- current_page_ancestor
This render method no longer has any of that logic: https://github.com/WordPress/gutenberg/blob/9122cc34fb1d972cdfc59614bf6f140a9b6f7d94/packages/block-library/src/navigation-link/index.php#L172-L295
And there doesn't appear to be an issue for this in the repo.