We have the same situation with Danone (100'000 employees) where we have several pilots. The broadest circle of the pilot has no Rep Link because it doesn't make sense, you need a Rep Link only if you have a super-circle working with Holacracy where you can process tensions limiting the sub-circle.
However, it makes sense to have an interface with the group because from the larger organization perspective, there is still a hierarchy with managers so the Chief Executive Finance has a role that interface with the group and triage any tension from the outside “world” to the appropriate roles inside and same in the other way. It's the same case for any organization as the world isn't in Holacracy and people thinks there is still a CEO.
Hope that helps.