On the other hand, your employer does not have the opportunity to accumulate your work without paying you while you are alive, then apply that accumulated work for fun and profit after your death. The "life plus X" is a Chesterton's Fence - it was originally there for a reason. The length of X has since grown to be ridiculous, yes, but posthumous publishing of works for which the creator received nothing was a thing.
Copyright in unpublished works is an entirely different matter than in published ones. Unpublished works get much stronger protection, that can extend for as long as 120 years from creation in the U.S. So I don't think your scenario is very relevant.
