I think you're now looking for conspiracies where none exists!
Congrats Greyfox, you followed on from me as the winner and I didn't (for the record) glean any answers from AB tho' I would shamelessly have done so if necessary. I would chalk it up as an AB win, however, because like you I wouldn't have known about it but for the link on here. As for beginner's luck, it was my second entry... so I guess that counts, too.
All crosswords make mistakes or throw up clues or solutions which are open to question now and then - why is this such a big deal?
The simple answer to why/how there can be a winner is that a great many people will have entered, giving the solution their best shot, and it wouldn't have been good enough to declare the comp null and void.
Sarumite is right: ask the magazine if you want clarification. But bear in mind that the editor's decision is, as they always say, final and that it's possible no correspondence will be entered into.
I can remember my answers to this one, btw - they were Goban Soar (knowing it was a probably incorrect variant) and Kilkea.