Right, but you’re still talking about a benchmark with a sequential transfer component.
Regardless of sata spec, with an SSD you’re not waiting 15ms for a disk to spin round to get your data.
As we’re on a bike forum, a relevant analogy:
A light bike will maybe make you a bit faster up a long climb, but the real difference is the nicer handling and sprightliness in all singletrack.
Even if you’re slow (sata3gbps) and so the time saved on the long climb isn’t as much, you still enjoy the nicer feeling and handling in the singletrack.