I was actually thinking of starting a thread about this quote myself but for different reasons.
The way this interaction is presented, felt like it would be setting up the major theme of the game, and from a sidelong perspective it does maybe play into everyone's personal quest
Wyl's choice between the contract and his father
Astarion's choice between himself and the sacrifices
Shadowheart and her parents
Lae'zel...trading a soul for the hammer?
Karlach and her choice between an eternal life in hell, or a brief one at home
Gale, and his choice to sacrifice himself
But a lot of that is circumstantial, and more about chosing others over yourself. Like Swen's response regarding the evil path, power is the draw, at the cost of fellowship.
But as far as the main plot goes, I see very little connecting it, or Withers for that matter, to the grand scheme at play. Which I'll be honest I don't totally understand.
Including the coda at the end with Withers, which just seems to lampshade the faulty reasoning behind the Dead Three's plan to mentally dominate worship.