777 Whatever,
They really aren't supposed to broadcast until 3 mile final but have to be "established" by 5nm, so the 5mile call is pointless and should be broadcast with inbound intentions at 10nm or 30nm.
Not so. Read CAO 82.3 and 82.5 and you will realise why at least some aircraft call at 5 mile final (and 15nm from the airport).