One-on-ones are the reason for that. Two people mean both are actively involved. Either listening to someone speak to them directly, or talking to someone directly.

> Teams that work together on the same project should regularly get together in a synchronous conversation.

This doesn't prevent that. It seems that it only prevents you from automating the decision on when to do that. If you need to synchronize, you can. However, if you don't, there is no need to hold a meeting. But people tend to make meetings opt-out rather than opt-in. This seems to enforce an opt-in approach first.