The real mystery is why Apple continued to sell cheap Macs with the more expensive auto-inject floppy drive for so long. The auto-inject drive is visibly more expensive, and the new case moulds were already in production, so why use a more costly part?

Perhaps there were warehouses stacked full of old drives, or pre-orders for new Sony drives. Perhaps drives and upper cases were deployed according to what was most readily available locally at the time of manufacture. Whatever the scenario, it implies that Apple's manufacturing process was in a real mess at that time.