Right, but they're flying them close on purpose - point is, at first glance it looks feasible and the close formation aspect has enough benefits that it's worth

Right, but they're flying them close on purpose - point is, at first glance it looks feasible and the close formation aspect has enough benefits that it's worth exploring further. For me, it's the first time I saw the idea to exploit constellations for benefit within the system (here, communication between satellites), and not externally (synthetic aperture telescopes/beaming, or just more = lower orbit = cheaper).