He's referring to the technical specifications printed (in very small writing) on the DNS-325 shipping box.
I looked very carefully at all sides of the DNS-325 box, which I still have since it was delivered only a few days ago, and I couldn't find any fine print mentioning this.
On the bottom side, it says:
1 Speed results may vary, depending on the benchmark utility, hard drive configuration, and the network environment used for testing.
"1" is found on the left side of the box:
High performance with Gigabit Ethernet connectivity 1
So the box doesn't promise gigabit per second speeds, and it doesn't say explicitly what speeds can be expected. Looks like they have hired a lawyer before printing anything on the box ;-)