FWIW:
Not understanding their photo mission, and thus what pics they were trying to take, one could still envision how one plans, and take precautions, if a given shot requires wing to be stepped down so that the picture is "looking up" at lead.
First thing, of course, is to recognize that it increases risk of lost sight etc.
If one is going to be "stepped down" as wing, the communications between lead and wing "where are you? - I am here!?" ("Two rotor diameters out at 4 o'clock, low" for example) has to be more frequent so that neither pilot loses SA, and so that maneuvers are made with sufficient safety margin.
As Fox pointed out, it is very important for briefing/planning, and the "go no go" decisions that the camera crew may hear need to be briefed to them, and explained why.
IMO, this would help the camera crew as they try to set up/frame their shots, if they know where their limits are.
Anyway, whatever internal comms were inside each helicopter, and between pilots, will be unknown until any CVR evidence comes to light.
Tragic loss of life
Some good points. I can image the reason for the 'stepped down' shot was to shot the rotor disc and backdrop, a flattering shot.
But if such close formation was deemed essential for the filming, why have the two aircraft full of ten people? Have as few people aboard for a shot like that. Better still, spend the money on a few hours of Cineflex and shoot an awful lot of B Roll from a safe distance and benefit from rock solid, safe shots of both helicopters.
I imagine there will be hell to pay for this, but it won't bring back the people.
So very sad.