MessagesInPerSec Metric Description

When observing the MessagesInPerSec metric (in BrokerTopicMetrics), it is noticeable that not all nodes receive the same number of messages (see attached image which shows a graph for the 4 nodes; message rate is (more or less) different on each node). One might think that this should be the case, since all data is replicated to all nodes.

However, I assume that the metric only counts the data that is written to the Topic/Partition Leader by a producer. And that the records that are written by replication between the nodes do not appear in the metric. Is this correct?