Venus JB put out imo an ott statement about the phones. It was just one of those instances where his response seemed 'off'.
Personally, I think the phones, Julie, even the silencer are all distractions in a way. The only definite facts we have are: they all died in the house; JB made a call; Sheila wasn't an experienced shooter. JB had entered the house through a downstairs window at some time. Both sides agree on those facts.
Sheila could 'possibly' have shot herself but everyone agreed she wasn't a competent shooter. Armed police in the US, have a less than 50% hit rate in live situations. Whoever killed the people in the house only missed one shot out of 24 or 25 with three targets who were adult, alive and (for two of them) moving. That's someone who can handle a gun. That means it wasn't Sheila.
If JB hadn't made the phone call then there could have been an argument for any of the people who would inherit being responsible . But JB made the call, blamed Sheila, said he had left a gun out (although staff and family said even if JB had left a gun out, Nevill would have put it away because the twins were staying). JB also admitted he had entered the house through a downstairs window (incidentally he said he did that after the murders but the police were monitoring him and knew he wasn't anywhere near WHF on those dates). So JB had motive, opportunity and the shooting skills.
It all feels incomplete because we don't know the timings, the silencer, the order of the murders. But regardless of all those aspects, from the basics that we do know and aren't disputed by either side , it all points to JB.