
The MSQ lays out a couple of ramifications of being flung forward: Legacy mark aside, you're also completely forgotten about by everyone you knew and loved in your old life! Barring extremely few specifics, all anyone can recall is a gleaming figure in their memory. Being cast forward effectively ended your old life, and no one even misses you.
As far as I can tell, Uncle Lou threw everyone forward because he wasn't convinced he'd have it in him to actually stop Bahamut and that was his contingency: People able to fight tomorrow if he failed today. It's a bit more complex than that, but that's the gist.
I don't think that Lou cast forward everyone who was present at Carteneau, but I might be wrong on this and don't have the resources to fact-check myself. I know for certain that the Legacy Warrior of Light coming in from 1.0 is a confirmed member of the Path of the Twelve and Circle of Knowing, and that pays forward to becoming a Scion in 2.0, but I'm not sure if the tattoo is supposed to reflect the entirety of the adventurers present then or just the ones "actually" in the main story.
As far as I can tell, Uncle Lou threw everyone forward because he wasn't convinced he'd have it in him to actually stop Bahamut and that was his contingency: People able to fight tomorrow if he failed today. It's a bit more complex than that, but that's the gist.
I don't think that Lou cast forward everyone who was present at Carteneau, but I might be wrong on this and don't have the resources to fact-check myself. I know for certain that the Legacy Warrior of Light coming in from 1.0 is a confirmed member of the Path of the Twelve and Circle of Knowing, and that pays forward to becoming a Scion in 2.0, but I'm not sure if the tattoo is supposed to reflect the entirety of the adventurers present then or just the ones "actually" in the main story.