And yet there was enough bodies left to let the WCouncil know that many of the Reds nobility was killed in the attack, as was all of Simon's household.
Easy to imagine how that could work out.
Pitched battle over a sizable battlefield, like a larger-scale version of the ghouls attacking the Warden camp in WN. The Reds over on one side, hit by a pile of ranged spells, lose their nobility leaving readily identifiable bodies. Simon's fortress, over the other side, blows up or collapses in on itself. Human remains inside it buried under hundreds of tons of rubble.
I do not believe that, with as much effort as the war is taking at that point, the Council could spare the wizards to go through the rubble looking for bodies.