I don't think you are. I was focusing on the action of the TXV in response to conditions across the coil, which airflow obviously is a major condition.Or may be I am missing something.
It strikes me as a combination of total heat load, airflow, and mass flow rate that ultimately dictate the outcome of evap superheat. Vary any one of these three factors and your superheat result will vary. Total heat load obviously varies throughout the day. Mass flow rate can vary by TXV adjustment, compressor pumping efficiency, cleanliness of condenser coils, cleanliness of liquid or suction line driers, length of lineset, restrictions, etc. Airflow is obvious...blower speed or return/supply restriction of whatever cause.