Roland Pulfrew, when we first flew formation in the VC10K back in 1984, the brief was to fly 'flat' in echelon in any turn away from echelon. So if you were in echelon right, a left turn would require a flat turn.
Quite where this daftness originated, I don't know. But as we had several ex-FJ folk on the course, as one we called "Bolleaux to this!" and from then on flew all turns exactly as we had in any other RAF aircraft. Had we flown 3 aircraft in echelon, perhaps a flat turn would have been necessary, but not for routine pairs formation.
In that A350 formation, it looked to me that the crew was looking up and out to confirm that they were adequately spaced during a formation break - not to maintain close formation.
Onceapilot, close formation breaks were part of the basic VC10K course and certainly weren't dangerous. They were fully briefed and flown to an SOP. The only 'dangerous' event I recall was when a pair of VC10Ks was breaking left on RW09 at Brize and some JATE C-130 cowboy decided to barge into the circuit between them from a downwind join.... Fortunately the no.2 spotted it and delayed his break accordingly.