The picture of the roundabout from above at the beginning of the article is extra confusing because it doesn't have the final lane markings yet and the ones you can see are misleading.
The (presumably) final markings[0] make things less confusing.
I was looking at the markings that are there, and they made it seem like traffic approaching the roundabout would have priority over traffic already on it.
What the hell is that "dump truck with trailer" on a really long connector at 3:50? Is that a thing in some parts? How does that navigate almost any kind of roadway safely?
They're called "pup" trailers [1] (example photo [2]), and the very long hitch exists for a few reasons: per-axle weight limit, respecting max weight capacity of smaller bridges, and ease of unloading [3] among them.
I was looking at the markings that are there, and they made it seem like traffic approaching the roundabout would have priority over traffic already on it.