No separation issue here, just keep 'em apart. At that close proximity, the wake wortex has not yet had a chance to spread, and the formation was planned using wake-vortex geometry to keep the a/c at a safe distance from each other. I got some pix from a colleague wherein the a/c were side-by-side, diamond formation, etc. - they wouldn't do it if it were unsafe.
Cheers, y'all.