Only VPN apps doing regular VPNs are allowed, obviously they have a performance impact, but that’s necessary for what they do. Anything using a VPN to implement other behaviour is not. Apps get judged on usability when it comes to system level concepts like VPNs all the time - keyboards are an example where there’s a lot more review for usability and “playing nicely”.
Not quite true. Charles Proxy uses a VPN in order to inspect network traffic, and that was approved. But I think in the general case what you said is correct and that Charles Proxy's approval is an exception.
True. I wonder if that’s because it’s explicitly a developer tool, and developers will understand what’s going on, and the risks/benefits of using a VPN.
I think the main reason they block apps using VPNs for other things is that it’s very easy for them to break internet on the whole phone with buggy software, and Apple don’t want lots of support time at the Genius Bar of turning off crappy ad blocking VPN apps.
It's probably partially that, and partially the fact that the VPN usage here is obviously beneficial. The information doesn't leave the device and it doesn't interfere with the normal workings of the apps (like ad blocking does). There's no reasonable complaint to levy against what Charles Proxy is doing. Versus ad blocking, which many people think is beneficial but which is clearly detrimental to app developers (especially when they end up blocking more than just ads, as sometimes happens).
