No, it appeared during the alliance with Admiral Ravensburg. Nothing in the text actually says it was built that time. In fact the text even says that before, during and after the Gothic War, it has never been defeated.
"For almost the entirety of the Gothic War, Eldar fleets were composed mostly of Escort ships accompanied by a few Cruisers. However, after the battle of Gethsemane and the alliance of many of the Eldar pirate fleets with Lord Ravensburg, a new terror was to hunt across the stars."
The paragraph says that during the entire Gothic War Eldar fleets where composed of Escort accompanied by cruisers, and that only after the alliance with Ravensburg the new ship "appeared".
Reading that paragraph I've understood that before that alliance the ship didn't exists at all (because it seems that the alliance with Ravensburg and the battle of Gethesmane are the two main events that led to the "appearance") ; but of course it isn't the only way of interpretation, I concur .
I thought that Ravensburg had borrowed them some Shipyards for the costrunction

I don't remember if there is something more about that events on Armada or some other book....