UW Control answers threats one at a time with Get Lost, No More Lies, and Day of Judgment, so Surrak, Elusive Hunter can't be countered and punishes their removal by drawing you cards, making it very hard for them to deal with profitably. Sheltered by Ghosts exiles a problematic permanent like The Theorist, Jace Beleren, while giving ward 2 to help a creature dodge their removal suite. Ba Sing Se is cut since it doesn't advance your board fast enough against a deck that will eventually out-value you with Countersculpt and Jace's Machinations, and Esper Origins' incremental plan is less important than resilient, proactive threats.