I have investigated and found that this is not related to only document records, it is happing for all approval where we have configured the conditions.
When the approval is set to Auto Approve, an approval task is in progress status. So, there is a delay between submitting the transaction to completing the transaction. Hence users see that message displayed.
We have also identified that only when the approval is set to Bypass, in that case, a message will not be displayed. And immediately data is committed to the database.
I hope this blog post was helpful for you. If you have any questions or feedback, please leave a comment below.