"If there IS bad news, CTP has to inform the market full stop....

"If there IS bad news, CTP has to inform the market full stop. They can't sit on the news or delay it just because it doen't suit."

But this is exactly what they've done a number of times in the past.
I don't think the volume is large enough to classify a duster though. It's likely that some people are getting out before the results, which triggered some panic selling. As soon as 5.1 was dumped into, jittery investors probably just sold out to minimise larger losses as the market depth became unfavourable.

If the well was a duster I'd say there would be more than 10million shares dumped.