Wx radar images displayed on the web can be 10-20 minutes out of date, I am told by the BoM. At the speed a line like that travels, it is a brave man who tries to correlate images of two moving objects between two websites.
Most of us fly-for-work types* have found safe ways to work around CBs. It looks to me like these guys were probably in VMC and (intelligently) were behind the line.
The Radar picture + BoM warnings+Facebook hype+the way it looks from the ground can all add up to deceptive.
The picture in the air is quite often very different to the way you imagine it from the radar image. You of all people Jaba would know that!
*fly-for-work and gotta go if possible, not to be confused with "having a choice to drive". I can tell my pax to drive but it doesn't put food on the table. If I can find a safe way to do the job without raising the risk of the operation, I will.