Wire EDM machine centers have been commercially available since the late 1970s. By the mid-eighties the machine tool and generator designs had changed dramatically. Unlike the early "sewing machines" the Wire EDM machining centers have developed into a machine tool.
The role of the toolholder in high-speed milling is really no different than its role when applied conventionally. The role of the toolholder is always to provide an interchangeable interface between a machine spindle and a cutting tool, such that the effectiveness of either component is not diminished.