The RAM slot helps for latency and throughput. SATA 3.0 would restricts this drive's read throughout from 880MB/s to less than 600MB/s, and would increase the write latency (5usec) by at least 1 or 2usec because of the typical CPU->southbridge->PCI express->SATA link it would go through, but here it is CPU->RAM slot. 1-2usec might sound negligible but it's not: it's 20-40% worse latency, so 20-40% fewer write IOPS.

SATA 3.2 (2000MB/s) would help for throughput but not for latency. It is also still quite uncommon even amongst latest generation servers, whereas this SSD is compatible with many current and older generation servers.