Realized that my assumption that the existence of a boolean field in the customFieldData table meant that it would be set to true (based on my understanding of how JW was using those fields) was not quite true; in fact there is a small handful of fields in which a boolean has been set to false. I've gone back through the data affected by my previous changes, and found three records which need to be fixed, so I'm going to fix those manually in both the live and dev dbs. Future scripts will take account of this by explicitly testing for true when converting values from custom fields to one-to-many fields.