That is true, there are a lot of things with upgrades in general; Security patches, configDB, Stats/ElasticDB, Yang changes etc..https://www.cisco.com/c/dam/en/us/td/docs/solutions/CVD/SDWAN/SD-WAN-End-to-End-Deployment-Guide.pdf(page 40)
Glad to help, but please read the statement below carefully.
"...why vManage and vSmart need to talk to vBond THE SAME WAY vEdges will talk to vBond."
in another words, vEdges will talk to vBond via VPN0, so the vManage and vSmart should.
