Well, the issue here is that your backup may be physically in a different location (which you can ask to host your S3 backup storage in a different datacenter then the VMs), if the servers themselfs on which the service (VMs or S3) is hosted is managed by the same technical entity, then a ransomware attack on that company can affect both services.
So, get S3 storage for your backups from a completely different company?
I just wonder to what degree this will impact the bandwidth-usage of your VM if -say- you do a complete backup of your every day to a host that will be comsidered as “of-premises”