The main traffic circle has been split up into 8 different segments, so that individual segments can have Relations added to them, such as the "Long Beach Transit 174" bus route. I'm new to mapping, so I don't really know what to expect, but it seems odd to split it up like that. It ends up adding noise to StreetComplete, in that I can't just say "yep, this traffic circle is asphalt", I have to go to a bunch of tiny segments and mark each one of them as asphalt.
I've also seen this for items generated from Lyft data, where a single road gets split into tiny segments so that one part can be marked as "no u-turn" or "no left turn". StreetComplete wants me to mark each tiny segment individually.
It's not compulsory, it's fine if you leave it as single circular road. But if you edit a bus route with Relatify it will automatically split the roundabouts to segments like this.
Note that route relation such as bus relations are added sometimes with entire roundabout without splitting it, that is also fine but splitting it is also fine and there is no consensus which is preferable
I think it would be more useful to regard this as a StreetComplete/editor flaw than an OSM flaw.
If you set the surface before the path is split, it's applied to all of them and many desktop editors have some sort of Ctrl-Select/multiselect support that makes this no real hassle.