Because any L36 suffering from hydrolock and being diagnosed by someone unaware of the manifold issue has probably been misdiagnosed as a head gasket.
Pat.. Please see the Regal GS post. Short version, no the ICM is fine. Our coils fire both posts at the same time. It's either both at once or bad coil.
My experience on where you are at right now is the cylinders are still wet. Pull the plugs and crank it over a ton, then blow them out with air and ensure your plugs are clean and dry.