I take issue with the “ideally have already read the paper” part. That’s actually not true for most of the attendees. There will be some who have, though, and those will be your co-authors or others who have helped you prepare it before the meeting. And they don’t mind waiting in silence during the reading period, because they have a stake in the outcome.
Also, 20 minutes of respite isn’t necessarily “waste.” Having 20 minutes of time to think deeply on something is often a gift!