Post author for revision not being set on update/insert

I’m trying to programmatically update a custom-type post with revisions enabled via form, and everything seems to be working fine except the post_author field for the revision is being set to 0 instead of the ID I’m passing in my array. All of the revisions get a 0, but the post itself gets the correct author ID. I’m not getting a WP_Error thrown either. It’s just ignoring the input. I’ve tried both wp_insert_post and wp_update_post with the same data, same results. The revisions and main post all save/create fine except for the post_author field in the revisions.

Relevant function code:

function yq_process_answer_submission_callback() {
// first check if data is being sent and that it is the data we want
if ( isset( $_POST["post_var"] ) ) {
        $params = array();
        parse_str($_POST["post_var"], $params);
        $name = get_userdata( $params['yq_author_id'] )->display_name;
        $posessive_name = $name.'''.($name[strlen($name) - 1] != 's' ? 's' : '');
        $title = $posessive_name . ' Response to Question: ' . get_the_title( $params['yq_question_id'] );
        $post = array(
            'ID'                        => $params['yq_answer_id'],
            'post_title'        => $title,
            'post_name'         => sanitize_title_with_dashes($title, '', 'save'),
            'post_content'  => $params['yq_body'],
            'post_type'         => 'yq_answer',
            'post_author'       => $params['yq_author_id'],
            'post_status'       => 'private',
            'post_parent'       => $params['yq_question_id'],
            'comment_status'=> 'open',
            'ping_status'       => 'closed',
        );
        if ($params['yq_answer_id'] == "") {
            $the_post = wp_insert_post( $post, true );
        } else {
            $the_post = wp_update_post( $post, true );
        }
        if (is_wp_error($the_post)) {
            echo "There was an error. Please try submitting again.rError message: ".print_r($the_post->get_error_message());
        } else {
            add_post_meta($the_post, 'to_instructor', $params['yq_send_to'], true);
            add_post_meta($the_post, 'instructor_notified', false, true);
            update_post_meta($the_post, 'to_instructor', $params['yq_send_to']);
            update_post_meta($the_post, 'instructor_notified', false);
            $response = array('question_id'=> get_post($the_post)->post_parent,
                                                'answer_id' => $the_post,
                                                'message'=>"Your response has been saved. It will be emailed to your instructor shortly."
                                                );
            echo json_encode($response);
        }
    die();
}
}

And also the init code for “answer” post type:

function create_yq_answers_post_type() {
register_post_type( 'yq_answer', 
    array(
        'labels' => array(
            'name' => 'Answers',
            'singular_name' => 'Answer',
            'menu_name' => 'Answers',
            'add_new' => 'Add Answer',
            'add_new_item' => 'Add New Answers',
            'edit' => 'Edit',
            'edit_item' => 'Edit Answers',
            'new_item' => 'New Answers',
            'view' => 'View Answers',
            'view_item' > 'View Answers',
            'search_items' > 'Search Answers',
            'not_found' => 'No Answers Found',
            'not_found_in_trash' => 'No Answers Found in Trash',
        ),
        'description' => 'Answers type for questions.',
        'capability_type' => 'answer',
        'hierarchical' => false,
        'supports' => array('title','author','editor','comments','revisions'),
        'public' => false,
        'has_archive' => true,
        'show_ui' => true,
        'show_in_menu' => true,
        'menu_position' => 25,
        'rewrite' => array('slug' => 'answers')
    )
);
}