Kafka transactions commit message consumability issues

Hello, everybody，

I'm running some tests while using Kafka transactions.

test 1 :
String msg = "matt test";
String topic = "test";
producer.beginTransaction();
producer.send(new ProducerRecord(topic, "0", msg.toString()));
producer.send(new ProducerRecord(topic, "1", msg.toString()));
producer.send(new ProducerRecord(topic, "2", msg.toString()));
for (; ; ) { }

test result：Messages also arrive at the consumer without delay.

My question is, why can data be committed without commitTransaction.

thx