Reverting to a previous build does not revert the tools-light vib version installed on the ESXi host.
Reverting an ESXi host is only valid if the host was updated using these methods:
VIB installation or removal
Profile installation or removal
ESXi host update using VMware Update Manager
Updated from a ISO
Reverting to an earlier version is not possible after upgrading to ESXi 7.0 due to partition changes to the boot device.
Note: To use an earlier version of ESXi after upgrading to version 7.0, create a backup of the boot device before the upgrade or reinstall the desired version.
Reverting from ESXi 8.0 to 7.0 is possible as there are no partition changes between the two versions.
Reboot the host.
When the Hypervisor progress bar starts loading, press Shift+R.This must be done while the bar is loading, not after.
Ideally, press Shift+R repeatedly once the "system is preparing to boot" message appears.
The following warning will show: Current hypervisor will permanently be replaced with build: X.X.X-XXXXXX. Are you sure? [y/n]
Actions such as ESXi upgrade/update or VIB installation/removal will discard the older (n-2) copy in the altbootbank folder and only retain the (n-1) copy.
After the first reboot following a successful ESXi host upgrade, if any changes are made, such as installing software VIB's that require another reboot, the option to roll back to the previous version will be lost.
After removing the host from Maintenance Mode, if the host is part of an High Availability cluster, the Fault Domain Manager VIB will be installed on the host. The Fault Domain Manager VIB does not require a reboot.