GP's not missing those edge cases; GP recognizes those edge cases are themselves a product of IP laws.

Those laws are effectively attempting to make information behave as physical objects, by giving them simulated "mass" through a rent-seeking structure. The case you describe is where this simulated physical substrate stops behaving like physical substrate, and choice was made to paper over that with extra rules, so that family can inherit and profit from IP of a dead creator, much like they would inherit physical products of a dead craftsman and profit from selling them.

It's a valid question whether or not this is taking things too far, just for the sake of making information conform to rules of markets for physical goods.