“Escape hatch” specifically refers to the speculation that Valve is positioning themselves in a way that they can’t be forced into paying fees for existing on the Windows platform, and that if push comes to shove they can say they only support Linux now. This hasn’t happened yet, but it’s a strategic stance which will likely prevent it from even beginning to happen. This doesn’t have to do with the Steam Deck specifically; it was also part of their intentions with the Steam Machine and etc.