Exactly.

Here's another simple way to think about it: Handling a request usually invokes a couple of layers of your code until you hit some IO - database, file system, network, etc. If that IO is done in a blocking fashion, this request is consuming server resources THE WHOLE TIME, even while it's doing nothing but waiting for a network response. On the other hand, if the IO is non-blocking (async), then this request consumes no resources while it's waiting.

So imagine you have a request that takes 2000ms to service, and 1700ms of that time is spent waiting on the database to fetch some data. Without async, that request will consume 2000ms of CPU time. With async, only 300ms of CPU time is used.