I don't know OpenEBS, but this isn't true of block storage systems in general. Both AWS and Google allow mounting virtual disks to multiple pods or nodes if all but one are mounted read-only.
Even multi-node writing is possible - see https://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ebs-volu... :
> Amazon EBS Multi-Attach enables you to attach a single Provisioned IOPS SSD (io1) volume to up to 16 Nitro-based instances that are in the same Availability Zone. You can attach multiple Multi-Attach enabled volumes to an instance or set of instances. Each instance to which the volume is attached has full read and write permission to the shared volume.
Google offers this too: https://cloud.google.com/sdk/gcloud/reference/beta/compute/d...
Of course this does have constraints compare to a true distributed filesystem, which the AWS page describes.
For that you need to use a cluster file system, but that's a different beast.
Kubernetes has specific support for this with its ReadOnlyMany access mode: https://kubernetes.io/docs/concepts/storage/persistent-volum...
However, I do see on that page that AWS EBS doesn't support this mode, so perhaps that's what you're thinking of.
Outside GCP, we do have an on-premise product that can deploy on any k8s cluster. In that case, the default is for the customer to provide an NFS mount for the data in question. We use the same k8s ReadOnlyMany access type for that.
Ceph(FS) and other distributed file systems allow you to access your data from any number of machines. Also they provide faster and more robust failover as they don't have to unplug the virtual hard drive and repair the local file system.