This is an interesting approach. By constraining the field it is trying to solve it makes grounding the natural language question in a knowledge graph tractabl

This is an interesting approach. By constraining the field it is trying to solve it makes grounding the natural language question in a knowledge graph tractable. An analogy is type inference in a computer language: it can't solve every problem but it's very useful much of the time (actually this is a lot more than an analogy because you can view a knowledge graph as an actual type system in some circumstances).