Laboratories - Appendix G Baseline System

G3.1.1, Exception "d" requires laboratory spaces with a minimum of 5000 cfm of exhaust to use a baseline system type 5 or 7 that reduce the exhaust and makeup air volume to 50% of design values during unoccupied periods. My interpretation is that the baseline laboratory spaces should be modeled as two-position (a constant occupied airflow and a constant unoccupied airflow equal to 50% of the occupied airflow). Does anyone disagree with this approach and think the lab spaces need to be modeled in the baseline as full VAV?