I think it's not really a ideal thing for client-side work and server side work to be separated (this is more a talent constraint). The most efficient organizations I have worked for are the ones that split themselves up into feature teams instead of strict front-end and backend teams. Otherwise, you end up with people waiting around for each other to make changes and that forces them to context-switch between different tasks (and everyone loses focus). Not to mention that the backend devs often dont get the interface 100% perfect the first time and you end up having to iterate over those changes - Which means more waiting around and more context switching (except if the required changes are minor in which case they can pair together).

With feature teams, you give people ownership over a feature of the software and they are responsible for bringing it to completion. The great advantage of fullstack developers is that a single developer can work on a feature end-to-end - It gets rid of communication problems, greatly speeds up development and reduces the backend-frontend "blame game" factor that you often see in large companies.

I like the way the article portrays people as concurrent processes but I think there is a fundamental difference between people and processes which affects things: People don't have perfect memory. When someone offloads a task to a different person and starts working on some new tasks asynchronously, when they come back to the previous task, they may not be able to resurrect all the old thoughts that they had the last time they looked at the same code (not the same level of depth). So they lose a bit of time getting back in the mindset.