The version control analogy in the description was spot on, but a good demo is worth a thousand words, so I will be waiting for a good demo to make conclusions.
1. https://reactjs.org/docs/concurrent-mode-suspense.html
2. https://reactjs.org/docs/concurrent-mode-patterns.html
I spent the last 48 hours writing them, and I think they answer your questions and contain many, many demos.
Does having an external state tracking system like Redux combined with a tracking a "loading state" solve the in-flight rendering item? My initial take is that this allows for a simplified model where data is loaded directly in components without the wrapping dance for tracking client load status.
That clock animation is pure genius:
But version control is a lot more approachable.