Surely sludge = friction?

While hearing Cass Sunstein talk about his new book Sludge, I thought surely this is fiction?

Not knocking it, I’m already known for saying friction can be a good thing.

One of the things I really like about the design guidance is the time to stop. A lot of the time we rush design in a frictionless way but we need to deliberately add friction.

Ian Forrester speaking at the ICO Privacy by Design 2021 conference