Isn't it ridiculously easy to set up attacks from within a "clean" network? It probably does increase costs marginally (you have to fly people to "clean" countries, set up ISP access with third parties, etc) but are there any public estimates how much it does that vs the increased costs to run this network? I would think it's marginal. Seeing the partner list this seems like more of a ploy by telecoms to attack tech…
Securing the routers and network cables removes the means for man in the middle attacks (or at least makes them preventable with router security). Not connecting to telecos does the same (because of bgp highjacking and the like).
Removing chinese apps and not storing data on Chinese servers makes decreases the amount of data that can be extracted from large portions of the population by the CCP. E.g. preventing the "who knows who" graph from leaking wholesale (even if individual nodes can still be investigated via other means).
This doesn't fix all security problems, but it removes some of China's current advantages in cyberwarfare.
Not putting apps in Chinese app stores and devices looks to be an outlier in that it's a form of sanction (in response to human rights abuses) rather than a defensive measure.