Re: I'm so glad we kept one!
From the vSphere product documentation for v6.7...
"The Virtual Machine Startup and Shutdown (automatic startup) setting is disabled for all virtual machines residing on hosts that are in a vSphere HA cluster. Automatic startup is not supported with vSphere HA."
From experience... Although you can sometimes go into a host's setting and configure startup/shutdown options, any settings you make for the automatic startup or shutdown of VMs will not work.
We get around it by having customised local.sh script that run when a host boots, to start some VMs for us.