well, I was thinking more in using more than one ES instances on the same machine listening on different ports, but your points on the other reply still apply.
Sadly at the time there was a big perf problem with indexingdocuments with 20kb+ binary blobs (non-indexed field) and so the change to 2 nodes vs one did have little noticeable effect on the throughput benchmarks I did with our data back then (~2015 ES 1.4) In the end I dropped this split and focused on the other bigger problems.
Would love to revisit this exercise with more of free time and better tools.