Why does base DB automatic Backups strategy not cleanup FRA

Summary:

We've setup a base db and configured automatic Backups. The backups are working, however our FRA eben though sized to 200GB cannot hold 30 days (which is our retention policy in OCI console) of archive log.

Content:

I wonder why this is designed this way. My first thought is that this is a bug, but an SR claims that this is intended behavior. It does not make much sense, does it? I don't see a reason why the automatic backup should not delete all backed up archive logs.

And what do you think would be the best workaround for this? I can't even edit the crontab of Oracle on the base db server which suggests, that this is not a good idea to have a script for delete all backed up archive logs there.