Just guessing...violent or suspicious deaths,perhaps,must be reported and "natural causes" deaths not.For example...my Mom died in the house that was our family homestead.She died of natural causes (cancer) and was sent home after all hope of a cure was gone.I'd guess that *that* type of death,at least,needn't be reported.
Forgot about the 3 year thing. In Ca. you don’t have to disclose if the person died of AIDS. Isn’t that special.