It is an effective way to counter aggressive pressing since few teams are comfortable pushing as many players forward as it takes to effectively press.
---CB----------CM---------CB---
-------------CM
FB-----------------------------FB
When you set up like that when pressed, it makes it very difficult to press successfully, because you have to commit so many players forward in very high positions. Especially so when the CM is as comfortable, and good at, as Xhaka is at hitting the long ball. If opponents still feel like pressing, then it will certainly give the likes of Özil, Alexis and Top Class Striker/Winger plenty of space to counter attack in.
For us, I can see it as a good option to mostly bin the dreaded way of bringing the ball forward when Per passes the ball to Bellerin, who of course immediately is put under pressure, only for us to lose the ball with the next pass. We manage a little better on the left with Monreal, but as a counterweight we then have Alexis there who too often loses the ball when he gets it with his back to goal.