vSphere70u1 - How can the vCLS agent VMs provide Clustering Service?
"so they cannot directly talk to each other" - there's more ways for VMs to talk to each other and to vCenters than just ethernet/IP.
Since DRS and HA were introduced they were essentially dependant on the vCenter being up - the VC decided what VMs to move for DRS and orchestrated the hosts moving them, and HA needed the VC to help coordinate the HA voting process and plan the 'failure map'.
vCLS allows for both DRS and HA to not only continue in the absence of a VC but also to allow HA voting and plans to evolve based on host availability with the VC in place. Think of it as the <7.0u1 VC DRS and HA functions shipped out of the VC into a three-way cluster to do this role for it - does that make sense?
Anyway just ignore them, they're effectively self-managed, by all means stick them in their own VM folder to hide them away but don't worry about them.