Does the Go standard library have unusually good TUI support or something? Am I just imagining the pattern of new TUIs being written in Go?
No, it really doesn't have anything TUI focused in stdlib. I get the reason why but it would be cool if they had something foundational in golang.org/x/
This project appears to be using github.com/rivo/tview which is is really solid.
The standard library doesn't have much for this, but Bubble Tea https://github.com/charmbracelet/bubbletea is behind many of the better Go TUIs. This one is using https://github.com/rivo/tview.
It compiles fast, starts up fast, and doesn't have a ton of hoops to jump through (ie borrower/checker in rust).