Seattle Department of Transportation and Washington State DOT have honestly gotten way too creative. It's like every city, every locale, and sometimes every street has a new collection of obstacles and rules to circumnavigate.
Roundabouts are great, but they should probably be round. In this case, it seems that it'd be easy to navigate if the two roads were brought into a single, simple roundabout intersection like you see at any other location.
The article explains why they made the decision not to do a traditional dog-bone interchange with two circular roundabouts. Namely, there were right of way limitations and a need to incorporate heavy farm trucks making a left turn. So, they ended up with basically 1.5 roundabouts which represents a simplification over the dog bone.
The lack of turn signal usage in the region also makes funky roundabouts much harder to navigate. Like you have to wait until there is a large enough gap in the cars to enter the circle, even if none of the cars actually end up intersecting your path.
It is intentional. The idea is to force drivers to reduce speed, and the mechanism is because it isn't familiar to the drivers. The claim is it forces them to be thoughtful.
Whether or not it works or is a good idea is not something on which I'm opining.
It's basically always safer to make a higher speed driver uncomfortable continuing at high speed. Reducing high speed through driver discomfort is 99% of what saves lives in road design.
Roundabouts are great, but they should probably be round. In this case, it seems that it'd be easy to navigate if the two roads were brought into a single, simple roundabout intersection like you see at any other location.