AWS RDS for SQL Server - Backup to/Restore from s3 - Multiple Account Scenario

Hi All,
I need a sanity check, and hoping someone here can provide it....

-Prod Instance - AWS ec2 instance running SQL Server (2022) in "Prod Account"
-s3 Bucket in "Backups Account"
-Dev Instance - AWS ec2 instance running SQL Server (2022) in "Dev Account"

Use Case: Need to be able to execute weekly FULL and daily DIFF backups from "Prod Account" to an s3 bucket in "Backups Account". Need to be able to RESTORE from those files into the dev instance in "Dev Account".

Situation: Prod instance can successfully backup to the designated s3 bucket FOR FULL BACKUPS. DIFF backups fail with "internal error". Policies and creds have been setup using the guidance from here (docs aws amazon com AmazonRDS latest UserGuide SQLServer.Procedural.Importing).

Additionally, no matter what we do, we cannot get the dev instance to read from the designated s3 bucket (same error; "internal error").

We opened a support ticket, and AWS say that the s3 bucket MUST BE IN THE SAME ACCOUNT as the ec2 instances. I do not see anywhere that this is a documented limitation.

Has anyone else setup their environment like this?

Any insight is helpful; thanks all!