With a teleprompter (or queue cards or notes) you are still speaking the words.

But with this system you are not. So it is more like a slideshow where your voice is pre-recorded per slide and you are pretending to speak.

I would still call a teleprompter a live setting. I wouldn't be surprised if Zuck had one. People can still stumble and maneuver and adapt in real time. Just like in a play. Rehearsal does not make the act not live. But if we want to get more fine grained there is a difference between a live demo and an on-the-spot demonstration. Think of it this way, people don't knock politicians for using teleprompters because they are lip syncing the words. They knock them for being overly rehearsed and not off the cusp. The complaint is actually beyond the teleprompter, the teleprompter is just a visual indication of this. But then imagine how people would respond if a politician went up on stage and pretend to actually speak but the words coming out were pre-recorded.

Or maybe we can meet more in the middle with something like autotune? I still don't think it is there because you'll still need to say the right words for autotune to work but even still people generally don't like that and feel like it is deceptive. So I might be being strict here, but we need to at least recognize that all these concerns arise from some form of deception. Where the expectation of what's happening doesn't meet reality.

No one will be upset if they never find out, but the real question is how they respond when they do. Does the person you're demoing to feel cheated, even a little, if you used a tool like this? I'd wager they would because they thought you were doing all the actions there in front of them.