Hi,
You can change the effective date using an Odoo server action. You also need to update the date
 fields of the related stock moves and stock move lines to match the 
effective date. Only then will the stock be reflected as processed on 
the backdated date(2023).
1. Settings->Technical->Actions->Server Actions
Type: Execute Code
Model: Transfer

2. Run
 the server action on the receipt corresponding to the purchase order by
 going to Purchase Order -> Receipt ->Action -> Stock Move in 
Backdate.

After running the server action, you will see that the effective date has been changed to the backdated value.

Stock Move

Stock Move Line

Hope it helps 
Hello,
Thank you for sharing, I'm trying to go live soon and you saved my day for past PO historic data.
But I still have the same problem fo Manufacturing Orders backdating. Would you have a solution for this as well? I don't see the Actual Date field on the form although I have the OCA stock_move_actual_date module installed which works very well with your above solution.
Thank you in advance.
Guess I couldn't find the right reply button, sorry.