Slowness with ure(4)

I recently upgraded from GigE Internet service to "Multi-gigabit" (aka 2Gbps) service. As part of that, I had a variety of machines that I wanted to get speedier access to. Most of them currently have igb(4), while one has a bge(4).

Anyways, the new interface comes up, the link comes up as 2.5Gbps correctly, etc. However, speeds tested using both iperf3 and the official Ookla speedtest CLI are both pretty bad. While the existing GigE interfaces have no problem getting 920-940Mbps, the ure(4) only gets around 420Mbps.

This made me curious, so I took one of the machines (a Late 2012 Mac Mini Server) and booted Linux, FreeBSD, and OpenBSD on the same machine. I got:

FreeBSD: 420Mbps
OpenBSD: 910Mbps
Linux: 2200Mbps

So it's clearly not hardware/network. I did verify that FreeBSD shows the device attaching to the USB 3/xhci bus. Any other ideas?

Thanks!

-Dustin