Factoid QA experiments: inferred relation ID is always 0

For the factoidQA datasets (FBQA and WebQuestionsSP), the "RelationID" field is always zero (which corresponds to the relation /location/country/form_of_government) and the hitter representation is computed based on that. https://github.com/microsoft/HittER/blob/main/hitter-bert.py#L233
Could you explain that?