Report said "many relatively modern production vessels, such as Essence, are constructed from
materials that are more susceptible to flexing under pressure. This, when combined with the larger windows that are commonly found in modern sailing vessels, makes the rebated substrate area around the windows more susceptible to failure." Seems they mean the vessel wasn't seaworthy.
So even if the storm covers had been fitted they would have needed substantial engineering attachment to stop them being blown out.