It makes sense that some of the criticisms wouldn't apply if you're not storing the files 1:1.

What about NFS or traditional filesystems on iSCSI block devices? I assume you're not using those because managing/scaling/HA for them is too painful? What about the openstack equivalents of EFS/EBS? Or Ceph's fs/blockdev solutions (although looking into it a bit, it seems like those are based on its object store)?