The con arguments for dart and go are quite similar. I cannot really derive the decision about the support status based on these arguments alone. To me this sounds more like personal reasons.
Elsewhere they have mentioned the UI is written in Flutter, which is completely Dart based. It seems as if this is what tipped the scale. Both are Google-developed languages, but one seems to be closer to the project.
They're used for pretty different things. Dart with Flutter is used for the UIs, which Go wouldn't really do well at, and for system services that's where the con list really comes into play.
I saw that too, but there is another bullet point about the implementation experience of trying to use Go to implement some system services. Sounds like they had a bad experience.
