I am on the Mobile site and saw no such warning. I was hoping for a general impression and I am quite disappointed that was included or at least not heavily marked out as a spoiler.
At least GB put the spoiler in the article, if you don't want to know about AC, then don't read about it.
Kotaku on the other hand, are buttholes. Sure, it's just a plot hook, but they removed any choice in the matter, would've been nice to be surprised.