Ann: Response to ASX Price Query, page-24

I don't disagree that that document can be a bit vague - but that is actually the guidance put out by ASIC - the body that regulates trading law!
Here's the actual Continuous Disclosure rules: https://www.asx.com.au/documents/rules/Guidance_Note_8.pdf

I guess the key to understanding confidentiality is that Listing Rule 3.1 only has a problem with such sensitive information, IF it is no longer confidential.
SNT have declared the info to the ASX and have provided assurances that the information is confidential, and the ASX has reinstated trade, so it would seem the ASX are presently satisfied that the information is confidential.

I would say it is common practice. You probably don't hear much about it because usually the first you see of such information is when the Company actually calls a Trading Halt when it is ready to release the prepared information they've had in their hands for the past days or weeks.