There is a bug in the VMware VCSA backup retention clean-up for VCSA 6.7 and 7.0. While the bug has been resolved for 6.7 in U3B, as of this writing the bug is still present in VCSA 7.0 as of U3F.
If you are using a Windows server as an FTPS destination for your VCSA backups, this script can be run as a Scheduled Task to enforce the retention policy clean-up.
Modify lines 2 - 9 for your environment and either run the script manually or via Scheduled Task to clean up older backups.