This is equally true with books. Trying to write everything you can think of as fast as possible isn't the same as telling your audience what they need to hear at the speed and depth they need to hear it.
To say "we have a lot to cover so I'm going fast" is a public speaking failure. It means you designed your material around *your* goal (quantity) not the *audience* goal (learning).
Covering is a bad metaphor. Just because you covered it doesn't mean anyone learned anything.