Well, while it is certainly unusual, I do not see anything wrong in having multiple interfaces with cluster management role. Of course, there could be just one routing table for admin SVM, so you really can only access one of them from different subnet.
From an installation perspective, it depends on the installation engineer as to which ports are used for cluster-mgmt but typically the favored port is e0a on this particular controller instead of e0M. Also, port e0a is the node-mgmt port as well which is fine. I've also seen customers try and use an ifgrp (e0a,e0b) for cluster-mgmt but there's no reason to do this either because 'cluster-mgmt' only hosts system manager and SSH traffic and in the event of a port failure, it will move over to a different port anyway. Can you provide the output of the 'net port show' command if possible?