I wouldn't say it's an illusion of choice, but rather it doesn't make sense the way it's framed. The player is misled into thinking it's Drifter vs Vanguard, but really the Vanguard has little issue with Gambit and there's no dialogue in game that suggests you're actually siding with the Praxic Warlocks. You boot up the game and are forced right away into the choice. I expected the questline to be what influences the player into picking a side, not the beginning of it.

So yeah, they intentionally framed it in a way that misled the players because they couldn't rely on an order of Warlocks with zero in-game development. Just feels very paper-thin and I don't appreciate the whole "Haha that's not what you actually chose." Feels cheap and lazy.