The specific test deployment was multitenant anyway-- you can't account or optimize for what tenants are going to index.
The impression I got was that they were trying to demonstrate for two specific workloads, how much more a single node of RS can do than a single node of ES, and that we should extrapolate the savings and performance if scaled out from there.
A properly deployed ES cluster versus a single RS node isn't a fair comparison either. It's a strained comparison in any case.
So in other words:
"If your specific use case is supporting 50,000 customers each having around 500 documents and only needing basic text search queries and relevance is not a major concern, RedisLabs Search might give you better performance than ElasticSearch!"
(This is assuming there isn't a different way to configure ElasticSearch to work for this scenario, that gives similar performance.)