Well, WooCommerce performs probably a lot more actions than just updating the $my_post['post_status'] when you work with Orders, and all those actions you will need to hook to your code which fires at cred_save_data()
But with this we cannot help, it's related to the 3rd party API.
If WooCommerce for example offers an API to fire a order or manipulate it with PHP, then you can use that within the cred_save_data() and it'll do what it would be supposed to do.
Toolset Forms is not intended to manipulate Orders, and even WooCommerce Products are a little restricted with Forms:
https://toolset.com/documentation/user-guides/creating-woocommerce-products-using-cred-forms/
Creating and editing Orders is totally another task, and usually, not needed as that is exactly what WooCommerce does, it provides a method to manipulate it's orders just fine.
When you "duplicate" this same to Toolset Forms, then you need to take in account all the "magic" that WooCommerce does for you in the background when you update the post_status of an order
With Toolset Forms you can for example send notifications from the form itself, when you edit the Form, you can add notifications and they will be sent at the set conditions.
But it is not suggested to do that, Toolset Forms is not intended to be a Front End replacement for WooCommerce.
The major focus of Toolset, or ability, related to WooCommerce, is it's design of Single Products and the Shop, and the payments you can add to forms with it, but it doesn't intend to "do what WooCommerce does in the backend" - in the front end.
If WooCommerce would/will intend that the Orders (or others) should be manipulated in the Front End, it would probably be of best quality if made by WooCommerce.
Toolset Forms is not a perfect choice for this as because it is limited in the interaction with WooCommerce's data structure, and does not integrate in such particular events like the Order Manipulation in the backend, unfortunately.
I can add a feature request, but I can tell that this has a lower focus, the major focus is on the design of the WooCommerce Data, and it's junction with Forms Commerce where you can cover payment on forms.
Please let me know if you know of any API that WooCommerce offers to manipulate the Orders "completely", we still help when it comes to troubles using that in a cred_save_data().