new PowerEdge R660xs USB speed

I'm working on a new PowerEdge R660xs server and have installed Ubuntu 22.04. Dell claims that the bottom rear USB port is "USB 3.0-compliant". However, "lsusb -t" reports it as 480M and running a speed test (using dd) gets around 300MB/s.

Is the port truly only 480M or am I overlooking something simple/stupid?