i think you might be right, but i've always had a bit of a different take: in short, i think he plays a bit of a dirty rhetorical trick with the word "communism". from what i remember he completely tosses out both the marxist and the historical interpretation of the term in favour of using it to mean a very broad, fuzzy, anthropological category of human relations, in contrast with "hierarchy" and "exchange". i think he does this both because the slogan "from each according to their abilities to each according to their needs" has such strong descriptive power, and to make the later point that while all these relations will exist in any given society, it's possible for any to be more or less dominant, and you could actually imagine a society where communism is the dominant form of human relation. the soviet union, for all its successes and lurches in the right direction, wasn't really that, and iirc that's graeber's take from the rest of his work

it still does bother me a little though, because i think he loses some of his potential appeal to communists who could learn a lot from his anthropology, and it's not like tossing the word communism into positive lighting ever gained much favour with liberals