Note that they state SATA II / SAS 6 GB. SATA and SAS are different protocols, so it is conceivable (but a little strange) to make an SAS backplane that can only support SATA II.
The two formats are not interchangeable, but an SAS controller can, for convenience, control an SATA drive. SAS is used mostly for enterprise applications; the drives are like the old SCSI drives (it's "serial attached scsi") in that they are smaller, more expensive, and more reliable. They can also be dual-ported to fail over to a second controller if the first fails.
EDIT: I managed to misspell "scsi" as "scis."