Ann: Trading Halt, page-106

A Trading Halt is required prior to a major announcement to provide fairness to the market.

You don't want to be off screen only to return 2 hours later to see that the share price has gone north or south and you didn't know big news was coming.

Also, if some risk that news might get out early and into the hands of a select few (for example, final stamping of documents, bank transactions etc. - that might mean that information can leak before the whole market are informed) then a TH is used to allow freedom to finalise the deal.

Therefore, by its nature, a TH announcement has to be very bland - it can't say "we are about to announce that we are [insert big news here] and want trading halted until we can..what?"

IMO
DYOR!!