Yes, this was one of the THEMIS rules discussed during the F2f
While folks definitely still disagree on this topic (as you can see from the above thread) the finally agreed upon consensus was CONCEPT_ID columns should be a CONCEPT_ID or 0 for everything except MEASUREMENT/OBSERVATION.VALUE_AS_CONCEPT_ID, MEASUREMENT/OBSERVATION.UNIT_CONCEPT_ID, MEASUREMENT.OPERATOR_CONCEPT_ID which can be NULL if data does not contain a value.