I am confused, you were an elder and didn't know what the proceedure for handling a DA person was?
An elder doesn’t get a DA case very often so they would be a bit vague on the procedures.
Normally they do wait a week or so in case the DA letter is rescinded. Believe it or not this does happen (though not usually in “apostate” circumstances). There was a sister who would habitually write DA letters every time she fell out with the elders or other brothers and then change her mind a few days later.
I would imagine in pps case because of his former elder status the local elders would be concerned about “endangering the spirituality of the cong” and so the announcement was made at the earliest opportunity.