Major We added MinDataServiceVersion as part of an update to our version negotiation primarily because (at the time) we returned results in the lowest format supported by the service, forcing clients to have to support old variants of the format even against new services. We changed the specification to say that the service must return the max version supported that is less than or equal to any max version specified in the client request, addressing this scenario.
The only place that mindataserviceversion is still useful is if a client is speaking to a downlevel service and wants to say "don't bother responding if you don't support at least version x".
We also return the version of the service in the metadata document, so (other than version negotiation for the metadata document) the client has a way to find out the version of the service and decide if it is willing to handle responses.
We can simplify the versioning story, and doc, by removing this extraneous versioning header.