Changing the MTU on vRPAs

I have a customer that uses 10Gb iSCSI for their connectivity from VMware hosts to Unity array. All of their iSCSI switches are set to MTU 9000. We are going to deploy vRPAs for RecoverPoint replication to the DR Unity. The vRPA documentation says to not change the default MTU of 1500 unless told to by support. Is there a reason why we cannot change the MTU to 9000 so it will talk to their existing iSCSI network?