That was my first thought, that a TUI is still a GUI. Close your eyes and explain how you can use a TUI from the keyboard. The only difference is what the display can render.

Modern GUI frameworks maintain a visual UI tree for on-screen interaction, and a semantic tree for accessibility features. You can find TUI libraries that do things like this, but for most TUIs, if you close your eyes and have the UI read to you, you're going to hear "dash dash dash dash dash dash bracket dash", because the fundamental concept of a TUI is in-band UI signalling.

For accessibility (the topic of this subthread), TUIs are not like GUIs.

I see, modern "GUI" programs aren't just GUI, whereas a TUI is just a GUI.

I don't think that's the right way to frame it. To me, in-band vs. out-of-band signaling is the real dividing line, and has been all the way back to PARC.