i mostly agree, and certainly didn't mean to slight darcs, bazaar and mercurial; darcs in particular was my version tracker of choice before switching to git
but i think 'the needs of Open Source collaboration' are somewhat more plastic and historically contingent than you imply. if you read producing open source software you'll see a snapshot of the dominant social practices of open source collaboration in the world git and bazaar were born into (which of course you also experienced, but others reading this comment may not have). those practices still survive in places, like netbsd and debian
arch, git, and family were designed to support a different set of social practices, practices that were at the time marginal in part because of the practical difficulty of applying them without software support. tom lord's radical program was to change the software landscape on which open-source collaboration happened in order to make those social practices viable
i agree that globally sequential revision numbers are incompatible with decentralization in the pre-nakamoto world, because they demand consensus, and decentralized consensus was infeasible until nakamoto. it's still probably too costly for this purpose