If it was unacceptable in 2013 then why did the website allow choices of "Friends" and "Internet Forum" for where you heard about the promotion from?
It was a fairly generic registration page, that allowed, among other things, you to sign up for public promotions. For signing up to a public promotion, 'Friends' and 'Internet Forums' were obviously valid answers.
Anyway, something changed inside IHG that changed their viewpoint of the whole thing. What that something was is a matter of conjecture....