SSO domain .local bad practise?

Hi

When deploying vcenter 5.5 SSO (or 6.0 PSC), for the SSO details the default is Administrator@vsphere.local

Is the "vsphere.local" a bad practise or is this the default? I ask as it just reminds me of the .local domain and I don't want to get in that trap again. Should the domain be  the AD FQDN?

Thanks!