Number one, any ferry driver can rack up thousands of miles each year and never leave the harbor, as can fair weather sailors, with nary a puff of wind over 25 knots, so "miles" don't impress me much.
Next, their boat is hardly an ocean racing foiling multihull, but rather a big waterborne floating hotel room with huge windows and I'm pretty sure not set up for sailing consistently in winds over 50 knots and certainly is [B]not [B] going to be flying along at 25 knots plus and probably nowhere near their expected 7.5 knots much of the time.
As this is supposed to be a voyage w/o the use of polluting fuels, how are they expecting to keep all their fancy equipment going without operating a genset? On the same note, what happens when they hit the common easterlies if they do take such a southerly course? Fall off and spend days going the wrong way, south or worse north, or crank up their engines?
No, their best shot at a quick passage under sail is by the traditional northerly route and as I said, even with a lifetime as a professional seafarer that is not a voyage I'd contemplate lightly, and certainly not without 3/4" storm boards over every window.
You clearly haven't seen their early videos. Riley was sailing solo, on an 80's Beneteau mono-hull he bought and fixed up. He admits that he didn't know fully, what he was doing, at first. He crossed the Atlantic a couple of times with that boat. He also has sailed in some extreme weather. On more than one occasion, he has cautioned viewers, to understand that most of their videos are shot during fair weather sailing, because, during storm sailing, they are usually too busy sailing, to do a video. He has stated this disclaimer several times. In one video, he made a point of setting up a couple of GoPros to capture some extreme sailing, to show some of what they hadn't shown enough of before.
In one video, he sailed single-handed from some island country, back to meet Elyna in Australia, and sailed through a storm. He described it in the end of the video, and apologized for not having video of it, explaining that he was busy at the helm, and managing the reefing of the sails, and couldn't worry about filming. But he included his description, because he didn't want non-sailors and novices to get the false impression that the cruising life is always the "smooth sailing" that their videos have made it seem.
When they got the Outremere catamaran, they were given some additional training in sailing the catamaran and motoring with a multi-engine boat.