I mean, honestly having the pause, or some other conformation that work was completed is useful. If you ever had a system 'fail successfully', finishing to fast does become a concern.
But that's the techy point of view. Most non-techies will probably prefer feel over functionality. I think most people do. If something is instant, it feels too good to be true. If something takes ages, you'll get bored or frustrated. While things that take a proportional amount of time feel satisfying.