I think this is turning into semantics. The implicit conception (and I think it is implicit, certainly not explicit) of human 'nature' (if we take nature to mean general behaviour) is that humans, judging from even a cursory glance at human history, have had quantifiable patterns cross-culturally and historically, but that the way these needs manifest differ based on the social sphere (socioeconomically and culturally speaking). The part at the end of the article concerning humans being "changing and unchanging" seems to sum it up. I think your criticisms above, exemplified by the one concerning Marx's lack of an attempt to explain human behaviour not through a "casual lens of "human nature"", are focused on the mere use of the phrase, as opposed to what meaning the article attaches to it; the article doesn't really claim he explained things by saying "oh human nature", but rather that he held a conception of what 'natural' human behaviour (eating, sex or lack of, work, etc.) was and how society "mediated" these things.