This is my best guess: I wouldn't really say they are redundant. It's more the way your current drivers represent the SATA controller, and the generic drivers for the PATA controller.
Going based off of this Windows representation, compared to the actual ports on the board:
For one pair of Primary/Secondary, it will probably appear (like in your screenshot) that only the Primary (2 devices) would be used, for the first two SATA ports. Then for the second pair of Primary/Secondary, it might appear that both the Primary and Secondary (2 + 2 devices) would be used, for the next 4 SATA ports. And in the case of the PATA controller, you'll probably find that again only the Primary (2 devices) would be used.
If you ever do RAID with SATA drives, or if you switch the SATA controller to AHCI mode, you'd probably be left with only one Primary & one Secondary (due to the PATA controller). The generic drivers seem to always assume there is a primary channel and a secondary channel, though there might not always be a secondary channel physically OR electrically present.