I think you're confused. Their description was precisely correct within the limitation of knowledge at the time. They certainly didn't imply that the mechanism was autonomously self-replicating (even though, thermodynamically speaking, that is correct).

  The replication complex is just an enzyme, it only speeds up things that are thermodynamically favored (replication can occur spontanteously because the dsDNA is lower energy, but it's rare because forming the phosphodiester bond requires a high activation barrier).

I think for some reason you are expecting them to pull the full replication complex mechanism out of their hat in the '53 paper but none of that is really necessary. What they described is precisely the mechanism; the proteins are just decoration to make the process faster and more reliable.