There are plans for Nimble to release VSS Synchronised snapshots for Hyper-V using the VSS writer. If you'd like to understand a more detailed roadmap timeframe for this please ask your local Systems Engineer.
Today we fully support snapshotting Hyper-V volumes with no VSS Synchronisation. This will mean that snapshots will be more crash-consistent than application or VSS consistent. Therefore today's Best Practice Guide for Hyper-V recommends to place application data volumes in separate guest-initiated volumes to the Virtual Machine rather than placing them inside a CSV volume if application consistency is required.