a windows desktop OS is limited of supporting up to 2 Sockes. Thats the reason why you only get 2 Threads within inside the GuestOS when assigning multiple vSockets based vCPUs instead of one and 8 vCores for example.
vSphere supports the vSocket configuration since version 4.1 but only by editing manualy the *.vmx. Support within the GUI comes later.
Regards,
Joerg