Am I missing something, or are they really boasting that they are able to schedule tens of jobs per second? ("Average pod throughput was 16.30 pods/sec") That seems very low...
Placing quality and throughput are always a tradeoff. Kubernetes, now, uses a naive algorithm that goes over all its nodes and finds the best placement. This is simple and effective for most web workload, when most of your scheduled jobs will take "forever" to run. And as it states in the blog post, after some simple optimization, now the scheduler can schedule tens of jobs per second. There are other limits make it slower overall. So we stop optimizing scheduler to avoid adding unnecessary complexity in its early days.