So why do we want to turn off the time sync in HyperV?
Because you want your domain controller to be the time sync, not the HyperV.
In SMB chances are that HyperV host is a workgroup, not a domain controller. Only a domain controller should be the primary time keeper in a SMB firm. So if you have a workgroup HyperV host that is not a DC and thus not advertising as the big kahuna of time for the domain, you therefore don’t want to keep that time sync box checked in HyperV.
You want the DC to be the time keeper.
Remember you can only be + or – 5 minutes off between workstations and the DC to connect to each other. Thus it’s very key to have the DC be “THE CLOCK” for the domain.