So, in dry conditions the rim brake bike was 2 seconds faster on average, but the guy said that was likely due to the aero advantage of the RIMS, not the brakes. He said the rim brake bike had more aero rims.
At the speeds described here, I think the rims would account for at least 2 seconds over 6 minutes.
So what I am getting from this is that it is a wash in the dry, but disc had a clear advantage in the wet.
Take away for me was that aero rims make a difference at those speeds.