Nomura has revealed that the marketing for Stranger of Paradise: Final Fantasy Origin was changed because fans already guessed that Jack was Garland.
When Stranger of Paradise was first revealed, there were a lot of different responses. Whilst many praised the game's combat, even more made fun of it through the chaos memes. There was also speculation as to the identity of Jack and his friends, as their modern-day clothing made it clear that the trio wasn't from the world of Final Fantasy.
After playing the demo, fans quickly began to speculate that Jack was actually Garland, the first boss of the original Final Fantasy who eventually becomes Chaos itself. There were several pieces of evidence to support this theory, including characters within the game saying that Jack and Garland use the same moves as one another. As it turns out, Jack is Garland, with Square Enix outright confirming the twist in the most recent trailer for the game.
In the closing moments of the trailer, Jack reveals that his last name is Garland and is seen covered in blood walking into the horizon. This should be seen as a pretty big reveal considering how much mystery was put into Jack's identity in the first trailer, but Square Enix is deciding to be upfront about the twist. As it turns out, that's very purposeful.
In an interview with Famitsu translated by aitaikimochi, Nomura says, "I was thinking of having Jack turn into Chaos. So why did we show [that] spoiler in the trailer? [...] I heard from Fujiwara we should release that spoiler since international fans already figured it out". The Famitsu interview also reveals that Nomura reworked the marketing to focus on how Jack became Garland, rather than the mystery of his identity.
You have to admire the upfront nature that Nomura and Square Enix are showing with the reveal of Jack being Garland. Not only are they showing it in the trailer, but Nomura is straight-up just spoiling what Garland eventually becomes too.