I've definitely seen this in real life, but recently I've started trying to actually watch when people use these interfaces, and they usually seem very slow - lots of hesitation, lots of mistakes, lots of repetition to do very simple actions. I watched someone use a terminal PoS recently and to clear a text input and insert a new value, she had to navigate to the start of the text box (no home key or anything like that), type new characters over the old ones, and then at the end delete any leftover characters from the previous input that they hadn't typed over. In a modern GUI, I would expect the user to have to (1) tab to the text box or press ctrl-A if they were in that text box, then (2) type the value they were interested in, possibly with typeahead support if it makes sense.

My working theory is that these terminal-based UIs aren't quicker because they're terminal-based, but rather users need to learn the keyboard shortcuts because they're so painful to use any other way. A well-designed GUI equivalent could be significantly quicker, and much easier to learn, but nobody wants to pay for that.