Spring Data Redis - StreamMessageListenerContainer only spawning one thread - spring

Question

I am using spring data redis to subscribe to the 'task' redis stream to process tasks.
For some reason redis stream consumer only spawns one thread and processes one message at a time sequentially even thought I explicitly provide a Threadpool TaskExecutor.
I expect it to delegate the creation of threads to the provided Threadpool and spawn a thread up to the Threadpool configured limits. I can see that it is using the give TaskExecutor, but it's not spawning more than one thread.
Even when I don't specify my own taskExecutor, and it internally defaults to SimpleAsyncTaskExecutor, the problem still continues. Tasks are processed sequentially one at a time, one after the other, even when they are long lasting task.
What am I missing here?
#Bean
public Subscription
redisTaskStreamListenerContainer(
RedisConnectionFactory connectionFactory,
#Qualifier("task") RedisTemplate<String, Task<TransportEnvelope>> redisTemplate,
#Qualifier("task") StreamListener<String, MapRecord<String, String, String>> listener,
#Qualifier("task") Executor taskListenerExecutor) {
StreamMessageListenerContainerOptions<String, MapRecord<String, String, String>>
containerOptions = StreamMessageListenerContainerOptions.builder()
.pollTimeout(Duration.ofMillis(consumerPollTimeOutInMilli))
.batchSize(consumerReadBatchSize)
.executor(taskListenerExecutor)
.build();
StreamMessageListenerContainer<String, MapRecord<String, String, String>> container =
StreamMessageListenerContainer.create(connectionFactory, containerOptions);
StreamMessageListenerContainer.ConsumerStreamReadRequest<String> readOptions
=
StreamMessageListenerContainer.StreamReadRequest
.builder(StreamOffset.create(streamName, ReadOffset.lastConsumed()))
//turn off auto shutdown of stream consumer if an error occurs.
.cancelOnError((ex) -> false)
.consumer(Consumer.from(groupId, consumerId))
.build();
Subscription subscription = container.register(readOptions, listener);
container.start();
return subscription;
}
#Bean
#Qualifier("task")
public Executor redisListenerThreadPoolTaskExecutor() {
ThreadPoolTaskExecutor threadPoolTaskExecutor = new ThreadPoolTaskExecutor();
threadPoolTaskExecutor.setCorePoolSize(30);
threadPoolTaskExecutor.setMaxPoolSize(50);
threadPoolTaskExecutor.setQueueCapacity(Integer.MAX_VALUE);
threadPoolTaskExecutor.setThreadNamePrefix("redis-listener-");
threadPoolTaskExecutor.setRejectedExecutionHandler(new ThreadPoolExecutor.CallerRunsPolicy());
return threadPoolTaskExecutor;
}