This is the route described in the article:
https://goo.gl/maps/X1enYAJ5kKD2And this is the shortest suggested route from Google:
https://goo.gl/maps/ee1Lppevpx42So it seems pretty clear they're taking a less than optimal route, perhaps to avoid the RFK bridge (that was the question I asked when the link was first posted). Using Maps measurement tool, it looks like the East River is less than 2000 feet across where the Williamsburg Bridge is. I don't know exactly where you'd end up measuring in that situation, but even with the strictest shiur for an amah, there's probably enough extra that it's not a problem. The individual spans on the RFK bridge are even shorter than that, but it's hard to know where to measure there.