This is more of a PHP question than a WordPress one but you could do the following:
function wp_template_lock_example() {
// Make an array of your post types
$post_types = array('subject-imposed', 'subject-free', 'dissertation');
// Loop the array and apply the template details to each.
foreach ( $post_types as $post_type ) {
$post_type_object = get_post_type_object( $post_type );
$post_type_object->template = array(
array( 'acf/text-introduction'),
array( 'acf/text-paragraph')
);
$post_type_object->template_lock = false;
}
}
add_action( 'init', 'wp_template_lock_example' );
Hope it helps!