You didn't mention that you had to install v2 first for the discount to apply.
That's not strictly true, it's just the easiest reply, since we might assume somebody wanting to buy KORD V2, would like want to try it first, considering it comes with a Trial.
The more accurate answer, is you must have the latest updates installed, meaning you must have ran ANY FSDT installer or just ran the FSDT Live Update. This would get you the latest version of the Addon Manager, which "knows" about O'Hare V2 ( if it's missing from the products list, it means the Addon Manager is outdated ) and, as long the new O'Hare is there, it CAN be purchased with a Discount, provided the original O'Hare is listed as "Active".
Installation and activation are always entirely separate things. The "installing KORD V2" step really means "be sure you have the latest updates", but KORD V2 can be installed before or after purchasing it, it won't make any difference to the availability of the Discount coupon.