What you say is true. That was the experience of Allied POWs in Germany. (Ersatz meaning substitute von Deutsch.) Ersatz became an English loan word for any inferior substitute.
But losing a boat-load of Arabica (Robusta, more likely!) would not have had an impact on British morale, military or civilian, like losing a boatload of Virginia long-leaf or (Heaven forfend!) Canadian rye.
And Churchill himself would have been bereft at the loss of a boatload of Cohibas!