I think this makes an assumption early on which is that things are serialized, when usually they are not.

If I complete a bugfix every 30 minutes, and submit them all for review, then I really don't care whether the review completes 5 hours later. By that time I have fixed 10 more bugs!

Sure, getting review feedback 5 hours later will force me to context switch back to 10 bugs ago and try to remember what that was about, and that might mean spending a few more minutes than necessary. But that time was going to be spent _anyway_ on that bug, even if the review had happened instantly.

The key to keeping speed up in slow async communication is just working on N things at the same time.