What makes you say/believe this? Both the Eastern and Western conference finals are listed as the same either/or Sunday/mid-week dates. I am not saying you are wrong necessarily, just wondering how you "know" the West gets Sundays and East gets Tuesday/Wednesday?
Conference Championships
Two-game series, aggregate-goal format.
Sunday, November 20 - Western Conference
8:00 PM ET Leg 1: TBD vs TBD Lower seed hosts FS1
Tuesday, November 22 - Eastern Conference
8:00 PM ET Leg 1: TBD vs TBD Lower seed hosts ESPN
Sunday, November 27 - Western Conference
4:00 PM ET Leg 2: TBD vs TBD Higher seed hosts ESPN
Wednesday, November 30 - Eastern Conference
7:00 PM ET Leg 2: TBD vs TBD Higher seed hosts FS1
http://www.mlssoccer.com/mls-cup-playoffs/2016/schedule