I don't think that these are metaphors but rather euphemisms. The purpose of the euphemism in this case is to obscure and dull the fact of our inevitable mortality
Yes, you are probably right. Both are figures of speech, but a euphemism seeks to dull the impact, whereas a metaphor seeks to disguise it. Calling a spade a spade is using a metaphor to focus on the opposite side of the general literal vs. metaphorical / euphemistic divide. But I still think we use metaphors to describe death and dying.