The behavior of the mirror.topics.whitelist is backwards incompatible. If some users currently have a whitelist setup with the old format (topic1:numPartitions1, topic2:numPartitions2), it is ideal to just rename "embedded.consumer.topics" to "mirror.topics.whitelist". Instead, this change forces those users to change their white-listed topics list to strip off the number of partitions. It would be ideal if the number of partitions is just ignored, with a little warning message. That way the change is backwards compatible.
If a user just renames "embedded.consumer.topics" to "mirror.topics.whitelist" and leaves the number of partitions, currently the corp replica behavior is to not mirror anything at all. That is unintuitive.