This an interesting point. When designing this I considered it to be more work for everyone manually editing files to add a 3rd field, which in addition increases the export file size without aiding the parsing of the file in any material way (given it's currently possible to disambiguate from the reference alone). Further, it creates additional complexity and increases the potential for mistakes due to typos. But easily sorting to differentiate between types is a good counterpoint - I'm just not sure it's worth the cost.