我对以下代码有疑问，请访问https://developer.wordpress.org/plugins/plugin-basics/activation-deactivation-hooks/#example

function pluginprefix_setup_post_type() {
    // register the "book" custom post type
    register_post_type( \'book\', [\'public\' => true] );
}
add_action( \'init\', \'pluginprefix_setup_post_type\' );

function pluginprefix_install() {
    // trigger our function that registers the custom post type
    pluginprefix_setup_post_type();

    // clear the permalinks after the post type has been registered
    flush_rewrite_rules();
}
register_activation_hook( __FILE__, \'pluginprefix_install\' );

为什么pluginprefix_setup_post_type 两个都需要调用init 和activation? 我尝试了一个示例插件，对调用pluginprefix_setup_post_type 在里面pluginprefix_install 并添加label 如下所示。

function pluginprefix_setup_post_type() {
    // register the "book" custom post type
    register_post_type( \'book\', [\'public\' => true, \'label\' => \'Books\'] );
}
add_action( \'init\', \'pluginprefix_setup_post_type\' );

function pluginprefix_install() {
    // trigger our function that registers the custom post type
    // pluginprefix_setup_post_type();

    // clear the permalinks after the post type has been registered
    flush_rewrite_rules();
}
register_activation_hook( __FILE__, \'pluginprefix_install\' );

代码也运行良好。我可以看到Books 在管理菜单中，一旦我激活插件。

那么，两次调用它有什么好处呢？