On the Swedish Apple site it says you can add/buy AC to Mac within 12 months & 60 days for iPhone & AC+.
Have no reason to believe it would be otherwise somewhere else on the planet.
As far as I remember it have always been like that for AC and Macs. Concerning iPhones I have no idea as I never had it.
That article was written over 4 months ago. Shouldn't that been corrected by now on websites if you could wait 1 year before buying AC+ for iPhone? And yes MacRumour had corrected their texts