So the above did not seem to work. While working on an unrelated item but of similar nature I was also unsuccessful, it actually created a looping rule. The rule below also does not seem to do what I was expecting, I wanted to back fill a reference to a Tenant table from RegularUser.
If RegularUser.TenantName (note: this is a shortcut to Tenants) IS UNDEFINED Then
FIND Tenants WHERE Tenants.ID=ThisRegularUser.TenantID
ThisRegularUser.TenantReference=ThatTenants
Can anyone confirm/refute that a rule or process can be used to create a reference? I feel like I might be missing something Obvious here.