Another point about some Leftist/Marxist critiques (or honestly just two Trotkist groups I know) of Graeber which is that he presents an alternative reading to what money and currency is to what Marx wrote in Capital.

This in my opinion kinda misses the point a bit that Marx and Graeber try to make. Marx worked in a way that he took in the current state of knowledge and the current research ideas - Smith, Says, Ricardo etc. - and then put them to rigorous testing, wrangled with them, added a bit, threw theories and counterexamples against them and looked at evidence (the amount of data and statistics Lening, Engels, Marx have done is impressive). For example the idea that there was a society which bartered three chickens for a cow and such and then there came longer lasting things like coins isn't quite what we have evidence for and yet Marx presents parts of that in his writings. Parts which were taken by Smith and adjusted. Smith invented those examples though and while those after Smith (and a bit Smith himself) did think that this is how money came to be I am skeptical that this is what Marx thought must have happened and that it is essential to Marx's theory that the way of how money/currency comes into being is unchanged.

I would on the contrary argue that for Marx analysis of how money/(currency)/capital work in Capitalism within his books it matters little. Since the tool and framework Marx used were analytical and somewhat static/statistical averaging for the system of industrializing capitalism and the development of it that he focused on. For the motivation and workings of capitalists it matters little whether currency came into existence as I-owe-you-staff-markings, coins you had to pay taxes in and only the occupying army had those tokens, or if you wanted something that lasted longer in your pocket than a dead chicken.