If we have four people on a life boat and food for three, morality must provide a mechanism for deciding who gets the food.
This is a distraction from you main point in at least one other sense: this claim is orthogonal to the claim that morality is not relative to economic conditions.

Yes, you correct that this was not an argument, simply my attempt to gesture at what I meant by the label "morality." The general issue is that human societies are not rigorous about the use of the label morality. I like my usage because I think it is neutral and specific in meta-ethical disputes like the one we are having. For example, moral realists must determine whether they think "incomplete" moral systems can exist.

But beyond that, I should bow out, because I'm an anti-realist and this debate is between schools of moral realists.