6) You must put your ETH Public address in the 'location' field of your Bitcointalk profile page. This address must match the address you submit in the airdrop form.
Is this a common practice? Why is this needed? Thank you.
Yes this is common practice for airdrops however, it isn't a requirement just for the sake of it. It serves as one of many ways to attempt to catch avoid scammers and multi accounts. The idea being that, if someone attempted to use someone else's BCT profile link to fill the form, surely they won't have access to change the profile field information, unless of course if the profile is compromised.