Fabien is trying to share the 4K display between the silent PC and the Macbook, but it is not possible through a single USB 3 hub due to bandwidth limitations.

Fabien is trying to share the 4K display between the silent PC and the Macbook, but it is not possible through a single USB 3 hub due to bandwidth limitations. The second image suggests that a separate display cable from each device fixes the issue, and the rest of the peripherals can still be shared through the hub. ...I should probably also read through the entire article, it does not end here :)