Severely low xG conceded doesn't mean "defend" more of the game, on the contrary it means you have a better control of the game. You are essentially allowing fewer opportunities for the opposition to have a glimpse of your side of the pitch. Teams that defend more, often concede a big xG, and if they have good defenders then their xG per shot would be lower. But yeah, pure low xG is all about controlling the game and the ball.

More balls but less penetration