I'm one of the authors. Seeing the Google presentation at CPPCon convinced us that the potential wins were worth the effort to productionize, but the similarity

I'm one of the authors. Seeing the Google presentation at CPPCon convinced us that the potential wins were worth the effort to productionize, but the similarity in the designs is a case of convergent evolution. Since then Google and Facebook have collaborated on a microbenchmark (https://github.com/google/hashtable-benchmarks/ https://github.com/google/hashtable-benchmarks/), which shows that the algorithms have slightly different tradeoffs but neither dominates the other.