I've just given it a try: works just fine with me.
But I did notice, that I chose virtio-scsi when I created the disk, don't now if that
makes any difference, but as an old-timer, I still got "SCSI" ingrained as
"better than ATA".
Chose FreeBSD 9.2 x64 as OS type while creating the VM (nothing closer appears in the
selection box), again don't know if there are better choices.
iperf3 shows slightly lower performance than a typical Linux guest, still rather close to
10Gbit/s on my network from the FreeBSD13 guest to a host "next-door", around
40Gbit/s VM to host.
Verfied usage of vtnet0/VirtIO NIC and vtscsi0/VirtIO SCSI via dmesg.