Really? Would you have some link to an article that mentioned this?
The game itself is proof enough.
It is an officially licensed "Pirates of the Caribbean" product.
It officially features Keira Knightly narrating; and the Black Pearl is named (even if she doesn't look like the real one).
The game ends with the skeleton crew of the Black Pearl repairing the sunk ship.
That means the story must take place before CotBP but after Barbossa mutinied on Jack.
Does this make the game...canon???
Technically it should've done, really.
But I don't get the impression anyone at Disney even remotely cares about any of it.
I'm not sure how serious they are about "PotC canon" in the first place.
The fifth film pretty blatantly disagrees with the second on how Jack got his compass.
So as far as I can tell, you might as well throw continuity right out of the window.
What is there to be canon with anyway?
There's some extra story in Legend of Jack Sparrow and the At World's End game; but I don't know how much.
There's a bunch of comics, including one short and very funny one that I cannot possibly fit into any chronology at all.
It has Jack and Will trying to open a chest while the cursed Black Pearl is chasing them.
Would have to be... DURING CotBP then? I don't think that makes much sense.
The only "true canon" thing I can think of outside the films should be the "Price of Freedom" novel.
Pretty sure that wasn't written to take the original 2003 game story into account though.
And I'm not sure how much it fits into the various comics either.
Or even the fourth and fifth films, which barely seem to follow from the events of the first trilogy anyway.
In OST, whatever happened to the EITC? How about Calypso?
She's at large gain, which affects a grand total of... basically nothing.
In other words: nothing matches with anything else anyway.
I wished there were some sense to be made of it all;
but any such attempt just makes my head explode.