The developer has never called it free to play--ArenaNet has been
trumpeting the fact that it will have no monthly fee for over 5 years dating back to before "F2P" was common in North America, but the two are not equivalent.
If forum posts or news outlets are claiming GW2 is F2P, they're misinformed. It wouldn't be the first time that people have misused terms they only loosely understand.
They could even be the same people who refer to the original Guild Wars as an MMO, another thing that ArenaNet never claimed (they labeled it a
"Competitive Online Role-Playing Game" instead).