The short answer for me is that the value stream will always encompass more of what's happening and what's valuable than DevOps, by the nature of the boundaries involved. DevOps involves Dev and Ops.
Value Streams are everything in the business, at every scale. That means that value stream approaches work equally well for HR functions, warehouse operations, patient intake, air traffic control, and making lunch. Technically the principles of DevOps work in many contexts, but those parts are just borrowed from Lean origins.
The shortest answer is that value stream approaches include all of DevOps, and much more.