How do we display a certain category type on a page while hiding all others?

Try this using is_single and query_vars rather than is_page:

add_action( 'pre_get_posts', 'change_queries', 1000 );

function change_queries ($query){
    if(is_single() && $query->query_vars['page_id']== 'your page id'){
        $query->set( 'cat', '3' );
    }
}