yes that is correct.  there are two different SMB communication paths and code  For the SMB clients talking to the VNX data mover it acts as a server and supports the SMB protocols listed with server_cifs. A client connecting to the VNX will usually negotiate the highest available SMB version that both sides speak (depending on client settings and GPOs) - so yes by default SMB3 capable Windows client will use that. If you are curious you can verify using server_cifs -o audit  For some administrative work like resolving SID's the VNX data mover talks to the domain controller and uses SMB secure channel. There it acts as a client and currently needs SMB1 available on the DC to work. This will change with an upcoming patch.  Note that in both cases the VNX is NOT vulnerable to WannaCry since we dont use the Microsoft SMB code that has the remote execution vulnerability and it doesnt run Windows OS so the executable wouldnt run there.
Is there any truth to this statement?  "VNX5300 needs SMB 1.0 enabled on the DC or kerberos fails between the VNX and the DC to authenticate all user access to the CIFS shares."  If I'm on code levels: Block-05.32.000.5.219 and File-7.1.79-8, does it use SMBv3 by default?  The output of command "server_cifs server_2" shows Max protocol = SMB3.0.
VNX5300 and SMBv1