Within the sentence "Orientation of the workpiece is defined by a kind of jig into which the workpiece is inserted", it's likely the word fixture will serve better than jig. As noted in the wikipedia Fixture (tool) article,
The main purpose of a fixture is to locate and in some cases hold a workpiece during either a machining operation or some other industrial process. A jig differs from a fixture in that it guides the tool to its correct position in addition to locating and supporting the workpiece.
The question refers to defining orientation of a workpiece; it does not refer to guiding the tool that operates upon the workpiece or guiding the workpiece against the tool. Thus, the device in question is more precisely a fixture than a jig.
It is untrue that "jig is the correct technical term for any bit of tooling designed to hold a workpiece for the purpose of facilitating a specific operation". Rightly, many machinists say fixture for devices that hold a stationary workpiece but don't guide a tool, and jig for devices that guide a moving tool or workpiece; others may use one term or the other for all such devices.