I suspected that it was something like that, and this is what I love about subsim. Simulation nerds with the commitment to realism and the willpower to forfeit saves, to refuse to use the event camera and prefer to just hear the torpedo explosions because they are running deep for a clean escape.
BUT...axxchor actually raises a good point: could this be somehow "modded in". The mod manages save games so as to only allow loading a save when the captain is certifiably alive. Like disabling all saves for a career the moment the captain dies.
You could get fancy and make it emit a DiD certificate like the ones people make for their captains, but something with some official weight for tonnage bragging rights.
I'm the furthest thing from a modder, and i wouldn't in a million years know what is needed for something like that. So for you modders out there, are these completely unreal requests? A DiD mod?