I have been watching the race myself and the winds & seas conditions encountered. What I see would be far from 'roaring' conditions. When you see 1 to 4 meter seas & average winds in the Southern seas you have good sailing conditions. The boats are making good progress on a daily basis. You can easily use the displayed race maps to measure distances between the longitude lines. My measurements indicate that the lines are converging the further South you go. You can see the indicated distances made good, according to the data sent back. It's also possible to see the track from the 2016 race that was completed on day 74. A study of the chart with the noon to noon positions marked is possible and distance measurements made. These all match the ballpark speeds of 16 to 18 knots. That is impressive for a wind powered vessel (blow boat). Many powered ocean going ships don't go much faster.
The bottom line that I see here is, if the earth is flat with a monopole model, then the race times & distances all have to be faked. Ocean currents are not a viable line of defense to make up the disparity between the required distances to be traveled on a flat earth map in 74 days. Yes, there are ocean currents out there, but they are fairly narrow and are only about 3 or 4 knots. The chances that a sail boat would both have a favorable current and a wind for a long time are about zero. There is no way to complete the race on a flat earth map in the time indicated unless the race data is being faked, or the earth is a sphere, as indicated on the race map. Use your best judgement as to which possibility to believe.