Earlier quoted context omitted.
Slack is slower. You can cover far more in a face to face meeting (or a video call) in less time. This is easily provable too. Have a 30 minute call with someone, and then have a 30 minute Slack chat with them. It becomes very clear that Slack doesn't work as well for that sort of comms. Slack is brilliant for asynchronous stuff, or very short chats, but it doesn't work for longer things.
Slack was just an example though. It could be a google doc. It could be anything written down. In what instance is talking about something better (I guess we’d have to define better but just assume better = retention) than reading about something? If I’m reading about it I can always read it again. In a meeting I’m going to forget 90% of it the moment I walk out the door (or end the zoom meeting).
That dynamic is much reduced in a synchronous meeting because everyone’s at the same meeting.