Risks of not upgrading the VM Hardware Compatibility versions to match the host?

[Oitsalan]

We have upgraded some hosts from 6.0 to 6.7, what are the risks of not upgrading the VM Hardware Compatibility versions to match the host?

[ShoHRock]

In my experience, Some virtual machine operations might be greyed out and unavailable. You might experience unexpected behavior in a guest operating system.

However, VMware does not recommend upgrading virtual hardware version if you do not need the new features exposed by the new version - https://kb.vmware.com/s/article/1010675