As a data point/anecdote, I had a parallel-port Zip drive with a 386 and Windows 3.1. I remember quite clearly that I had to load a SCSI driver in CONFIG.SYS. I didn't understand back then why I had to load a SCSI driver for a parallel port device, years later I found out that the parallel port version was actually the SCSI version but it tunnelled the SCSI protocol via the parallel interface...