Gvim is a TUI with a GUI taped on top, and whilst the PowerShell you've given there does call a GUI library function as described, I'm pretty sure the author is

Gvim is a TUI with a GUI taped on top, and whilst the PowerShell you've given there does call a GUI library function as described, I'm pretty sure the author is referring to non trivial examples of a GUI like sublime or VS Code.