But it does mean something true. If “Kanon is dead” doesn’t mean “this particular human being’s living body ceased to live and is now irreversibly dead”, then it certainly means something else. That’s the whole “Red vs. Blue” game: that’s why Erika started demanding further definitions. If I recall correctly, she did get further clarification on the definitions of corpses and the like later on, eliminating this kind of possible use of the word (maybe not for corpse, but for something anyhow). It’s a game of working around ambiguities.
Even if “X is dead” always used a different definition of dead: then at least you know dead was used in a different way. It still gives you some knowledge - just ambiguous knowledge, which can be further refined.