In vsan cluster in that process of stop and start, I think that the version after 6.7U3 will need the following command before and after
stopping and restarting vsan cluster.
python /usr/lib/vmware/vsan/bin/reboot_helper.py prepare
python /usr/lib/vmware/vsan/bin/reboot_helper.py recover
Are these scripts just doing a health check? Or is it a command that also internally restarts the VSAN?
No, it is more than a healthcheck. this script ensures that all components on the vSAN cluster will be available after the full cluster power down. This script is only needed when you power down the full cluster at once though! When you do an upgrade (one by one) and use "ensure accessibility" when initiating maintenance mode you don't need to use this command.