I believe CC charges don't mean anything, because if an airline want to cancel, it will just refund the money and that's it.
However, due to the fare rules posted, the limited travel period, etc., my idea is that this one was a weird but intentional flash sale/promo. In any case, I am not worried in the least... what will be, will be
I am only sorry that the limited time window for BLQ-HKG, plus only Wednesday and Saturday departures/arrival, didn't allow me to book a trip for the whole family.