It doesn’t trigger when a ship is scuttled because of a fire mast, right?
Correct. You must reveal it immediately after sinking an enemy ship. For the purposes of the event, the ship doesn’t get credit for the sinking retroactively from the scuttling. (especially because that scuttle can be avoided if the ship can row to safety/etc)
You may reveal this event immediately after one of your ships sinks an enemy ship
It is sunk by a hit, scuttling removes the sinking attribution from the ship effectively doing the sinking. (starting to go on a Captain Jack ramble XD)
(99% sure, hopefully Woelf will confirm)