"The CPU resource shares for (vm you are trying to move) are much lower than the virtual machine's in the resource pool. With its current share setting, the virtual machine will be entitled to 2% of the CPU resources in the pool. Are you sure you want to do this?"
The workaround I found is to merely view (without changing anything) the Resouces settings for the VM: Right Click VM->Edit Settings...->Resources Tab -> OK
vCenter reports Reconfigure Virtual Machine (but we did not change anything!)
However, there are other variations of the message where this workaround does not resolve the message (eg "much higher" or memory instead of CPU resource) - this will be worth opening a case to resolve these other cases