It's possible that commenter is misguided. The documentation on NETunnelProviderManager[1] says it needs the extension and that you should send an email to get it, but there's no indication as to whether there's anything stopping you from granting yourself this entitlement on a development machine (obviously Apple needs to approve it for an app on the MAS; I don't know what limitations there are for non-MAS apps in this regard).

[1] https://developer.apple.com/library/prerelease/mac/documenta...