It is, sort of, but it only shows part of the picture. I'll explain. Yes, TechEmpower will show you some of the fastest servers / frameworks. Maybe you can get close to a million requests per second in some of the native servers delivering static plain text / json on top of the line hardware. Eventually though you need to build and ship an application and some software that does more than a few queries.

High performing/scalable systems are built from lots of pieces of interconnected software like caching software (Redis, memcached, etc), work/job queues (RabbitMQ, ZeroMQ), asynchronous database queries and probably other things? The way these pieces fit together make much more of a difference than the server / framework you pick. I'd say it doesn't largely matter which Python framework you choose when you still have a blocking SQL query that has to be done on each request. The difference will be microseconds compared to how long that query takes.

It is important to benchmark/profile though. Maybe not at the framework level but as part of the continuous integration process. Determine what parts are slow, what parts could be replaced with asynchronous / event based code, and what parts should be replaced with something written in native code (C, Go, or Rust I guess) especially because Python makes it easy to integrate directly with native code (at least in C, I don't have experience with Python talking to Go or Rust).