Must be behaving differently on the different generations of iPhone, or something else different about our setups. I was using the iPhone 6 for Runway HD, with collision aware running on the iPad, I'll maybe try with everything on the iPhone and see if it still looks ok as well.
I still don't know if Runway HD gives collision warnings, or just shows the traffic. I was on the ground today a few hundred metres from a hovering helicopter with ADSB which showed up OK, but I didn't get any warnings, although I wasn't moving so don't know if that would inhibit any warnings.