These descents were in Class G airspace, 118.2 or 122.1, and require a broadcast prior to TOPD. The way I understand it is you;
1. Call centre and get traffic advisory prior to top of descent.
2. Make an all stations broadcast advising descent particulars. This requirement is specifically for the benefit of VFR traffic.
This is not an isolated incident, it occurs all the time in class G in FNQ. Pick any frequency, 118.2, 122.1, 120.3, 118.6, 134.65. Those that are doing it possibly don't realise their errors, as it sounds just the same as all the other calls made in class G.
The other downside is when you question these "professional" pilots as to their location, you get treated with disdain as you are "only a VFR pilot."
I specifically remember talking with turbo prop driver to arrange separation inbound to a port and advised I was on a particular radial at 25 miles, passing 4500ft, only to be questioned "Are you sure you are south-west of the field?" FFS, I have in excess of 5000 hours and seven IR renewals and been flying more than 12 years. I'm pretty sure of the difference between a radial and a bearing.
Time for another Red,
Two Dogs