It's easy to see the difference with examples. A good example of clear speech is Sam Harris. Even when debating contentious topics, he speaks in calm paragraphs.[1] I could imagine Harris behaving the same in a one-on-one conversation. Contrast that to his opponent, William Lane Craig.[2] If Craig spoke that way in my living room, he would appear insane.
Avoiding filler is necessary for oration, but it's not remotely sufficient. I think this app will improve people's ability to communicate, not bloviate.