C&P from my original request (OSP-31886), which was archived and apparently not migrated here:

Formally requesting the enhancement to allow volume resize as an online operation. Aside from the main benefit of adjusting storage capacity on the VMs without requiring shutdowns, data migration or any other manual task, being able to extend volumes online allows keeping VM homogeneity and configuration consistency.

In the customer's use case, they add volumes to VMs as space is required, which means that multiple VMs running the same workloads end up having different count of disks of different sizes, depending on when they were built.