WebCenter is a CA NetMaster product too and it monitors network performance and diagnostics using the UDP port. CA OPS/MVS does not use the UDP port for OPSWEB.
The CA OPS/MVS WebCenter portion of the product is based upon the CA NetMaster WebCenter feature. NetMaster must open a sockets interface in order to create the OPSWEB server. As you have seen, there is the OPSWEB port that is in LISTEN state, and then you'll see that UDP ephemeral port. This port is required for the sockets Domain Name Resolution (DNR) support.
The UDP ephemeral port is required for the sockets DNR support. Sorry, but there's no way to disable that. And as seen, it is an ephemeral port that can and will change. We have no control over that.
Sorry, but in order for DNR protocol to work under the sockets interface, we must open that UDP port, of which the IBM sockets API we are using, doesn't allow for a hard specification.