Here is what I got from them this time. It's a little different from the reply I got the first time but it basically says the same thing.
Dear Valued customer,
You have reached Microsoft Customer Service, South East Asia. My name is Rizky and I would address your enquiry. As I understand it, you have inquiry for Microsoft Windows 8 Pro from G2A website. If my understanding is inaccurate, please let me know.
For this information, we have to inform you that it is not recommended by Microsoft to make purchases of these softwares as they are not official and genuine versions that are support by Microsoft activation. Microsoft does not have any vendor agreements with G2A or any of it’s resellers and so this in direct conflict to the Microsoft software license agreement since they are not an authorized electronic supplier of genuine Microsoft software. We cannot verify the genuine sales of the G2A third party seller but without authorization from Microsoft they cannot be genuine supplier.
Sincerely, it was a pleasure helping you. If ever you need further assistance please don’t hesitate to send us an email and we will be more than happy to help you.
Thank you for contacting Microsoft. Have a nice day!
Regards,
Rizky
Customer Service Representative
Microsoft Customer Service, South East Asia (SEA)