Possible performance improvement with tokio spawn inside main

[yanns]

From https://users.rust-lang.org/t/why-tonic-not-good-in-beckmark-of-multi-core/70025/6

One of the things that's hurting Rust's performance in that particular benchmark is that the accept loop is running directly inside a call to block_on. This can be a performance problem because a tokio::spawn task will never run on the same thread as a block_on task, which means that all connections must be transferred to another Tokio thread before they can be processed.

As far as I understand the code, I think that we're good here, but I just want to make sure it's how I understand it.

The main is using block_on as excepted:

    let runtime = builder.build()?;
    runtime.block_on(Executable::builder().start())

This is waiting for RouterHttpServer

        let router = RouterHttpServer::builder()
            .is_telemetry_disabled(opt.is_telemetry_disabled())
            .configuration(configuration)
            .and_uplink(uplink_config)
            .schema(schema_source)
            .license(license)
            .shutdown(shutdown.unwrap_or(ShutdownSource::CtrlC))
            .start();

        if let Err(err) = router.await {

and this is using spawn:

        let listen_addresses = state_machine.listen_addresses.clone();
        let result = spawn(
            async move { state_machine.process_events(event_stream).await }
                .with_current_subscriber(),
        )