I still didn't understand why one needs to prove their ownership when they already set up their email ID in their account?
Unless if they didn't set up email id and ask for support help then they can ask these questions but OP mentioned that he had set up email in his account but still went through this process of proving his ownership.
I had my two factor authentication enabled and still i was not able to prove my account the first time around as they promised to follow up with the details in my mail ID and i did not get any mail from them and after a couple of days i had to contact them again and verify the details once again, i was not active in the site for a while and so it was hard to find my old transaction details and IP address i was using a year back , but luckily i found them from my old hard disk, if not for those transactions and logs i do not think i would have got my account back.