Spring Cloud Stream - Reactive Binder Concurrency Issue

Simple SCS repro.

Pre-requisites

Create a topic called "test"

Versions

Spring Cloud Stream: 4.0.2 Boot: 3.0.6

Describe the issue

The Reactive Kafka Binder documentation suggests it should be possible to set consumer concurrency above 1.
The binder should then create the correct number of KafkaReceiver as per this value.

Given this config:

    stream:
      bindings:
        test-in-0:
          destination: test
          binder: reactorKafka
          consumer:
            concurrency: 2

An error is thrown:

Concurrency > 1 is not supported by reactive consumer, given that project reactor maintains its own concurrency mechanism. Was '...test-in-0.consumer.concurrency=2'

This is contrary to the documentation.

Root Cause

The FunctionConfiguration class still contains this check, which doesn't seem appropriate if the binder is the new Reactive one.

    if (consumerProperties != null) {
        function.setSkipInputConversion(consumerProperties.isUseNativeDecoding());
        Assert.isTrue(consumerProperties.getConcurrency() <= 1, "Concurrency > 1 is not supported by reactive "
                + "consumer, given that project reactor maintains its own concurrency mechanism. Was '..."
                + inputBindingName + ".consumer.concurrency=" + consumerProperties.getConcurrency() + "'");
    }

If the check is removed, then everything seems to work as expected with a new ReactorKafkaBinder created as per the concurrency setting.