WordGrinder and Finch are user interfaces though? How is that "Without a GUI"?
Not as awesome as CLI, which features stuff like user action history, but you still get to use the terminal, so you get stuff like being able to use it inside `tmux`, or recording what's happening with `script`, or copy any text without the interface being able to disallow it, or pasting a generated set of user actions (when you skip terminal pasting protections) to automate your use of the program, or being able to safely automate its use with something like tk's `expect`, which allows you to factor-in whatever the program outputs (something you can't do with GUI without something like OCR).
CLIs are much easier to automate, though.
The requirement for a Graphical UI (GUI) is that the user interacts with it via graphical icons and visual indicators. These can exist within a terminal. So, personally I would say WordGrinder and Finch are GUIs in this literal sense. However, your typical lay user may not interpret it this way.
TUI is a sort of abstract term. Sometimes people mean Text UI and sometimes people mean Terminal UI. I don't think these are mutual exclusive. I would understand a text-only UI to be without any visual indicators, whereas terminal UI could be either text or visual. I guess its also worth noting that the phrase 'TUI' was coined after 'GUI'. Perhaps TUI was coined to differentiate the traditional GUI application (a window drawn on a screen with sliders/buttons) from the traditional terminal application (text-only commands). But nowadays, we have libraries like ncurses, that allow us to draw things within a terminal.
--
[0] - Almost; some modes use "graphical" indicators like horizontal lines which are really just decorations. You can mess with them if you try hard enough, but by default they'll be ignored by usual operations like navigation, search or copy/paste.