VDP 6.1.3 - ESXi 5.1 Compatibility Issues

The VMware interoperability matrix says VDP 6.1.3 is compatible with ESXi 5.1. However, if you backup a VM when VDP is running on a 5.1 ESXi it will fail. I tried this with the following setup.

I deployed a 6.1.3 VDP on an ESXi 5.1 Build 1065491 and created a virtual machine on this same host. Then, I ran an on demand backup for this VM and it failed immediately. The backup job log had the following entry:

2017-01-04T21:13:36.723-05:-30 avvcbimage Warning <16041>: VDDK:SSL: Unknown SSL Error
2017-01-04T21:13:36.723-05:-30 avvcbimage Info <16041>: VDDK:SSL Error: error:14077102:SSL routines:SSL23_GET_SERVER_HELLO:unsupported protocol
2017-01-04T21:13:36.723-05:-30 avvcbimage Warning <16041>: VDDK:SSL: connect failed (1)
2017-01-04T21:13:36.723-05:-30 avvcbimage Info <16041>: VDDK:CnxAuthdConnect: Returning false because SSL_ConnectAndVerify failed
2017-01-04T21:13:36.724-05:-30 avvcbimage Info <16041>: VDDK:CnxConnectAuthd: Returning false because CnxAuthdConnect failed
2017-01-04T21:13:36.724-05:-30 avvcbimage Info <16041>: VDDK:Cnx_Connect: Returning false because CnxConnectAuthd failed
2017-01-04T21:13:36.724-05:-30 avvcbimage Info <16041>: VDDK:Cnx_Connect: Error message:
2017-01-04T21:13:36.724-05:-30 avvcbimage Warning <16041>: VDDK:[NFC ERROR] NfcNewAuthdConnectionEx: Failed to connect to peer. Error:
2017-01-04T21:13:36.742-05:-30 avvcbimage Warning <16041>: VDDK:SSL: Unknown SSL Error
2017-01-04T21:13:36.705-05:-30 avvcbimage Info <16041>: VDDK:NBD_ClientOpen: attempting to create connection to vpxa-nfcssl://[datastore1 (2)] Thick/Thick.vmdk@10.109.10.171:902
2017-01-04T21:13:36.723-05:-30 avvcbimage Warning <16041>: VDDK:SSL: Unknown SSL Error
2017-01-04T21:13:36.723-05:-30 avvcbimage Info <16041>: VDDK:SSL Error: error:14077102:SSL routines:SSL23_GET_SERVER_HELLO:unsupported protocol
2017-01-04T21:13:36.723-05:-30 avvcbimage Warning <16041>: VDDK:SSL: connect failed (1)
2017-01-04T21:13:36.743-05:-30 avvcbimage Info <16041>: VDDK:DISKLIB-DSCPTR: : "vpxa-nfcssl://[datastore1 (2)] Thick/Thick.vmdk@10.109.10.171:902" : Failed to open NBD extent.
2017-01-04T21:13:36.743-05:-30 avvcbimage Info <16041>: VDDK:DISKLIB-LINK  : "vpxa-nfcssl://[datastore1 (2)] Thick/Thick.vmdk@10.109.10.171:902" : failed to open (NBD_ERR_NETWORK_CONNECT).
2017-01-04T21:13:36.743-05:-30 avvcbimage Info <16041>: VDDK:DISKLIB-CHAIN : "vpxa-nfcssl://[datastore1 (2)] Thick/Thick.vmdk@10.109.10.171:902" : failed to open (NBD_ERR_NETWORK_CONNECT).
2017-01-04T21:13:36.743-05:-30 avvcbimage Info <16041>: VDDK:DISKLIB-LIB   : Failed to open 'vpxa-nfcssl://[datastore1 (2)] Thick/Thick.vmdk@10.109.10.171:902' with flags 0x1e NBD_ERR_NETWORK_CONNECT (2338).
2017-01-04T21:13:36.780-05:-30 avvcbimage Info <16041>: VDDK:NBD_ClientOpen: attempting to create connection to vpxa-nfcssl://[datastore1 (2)] Thick/Thick.vmdk@10.109.10.171:902

The VDDK disk release on 6.1.3 VDP is:
2017-01-04T21:13:27.244-05:-30 avvcbimage Info <16041>: VDDK:VMware VixDiskLib (6.5) Release build-4241604