If I recall, when the Eaton Centre facade was redone in the 90s, the idea was to create the illusion of different buildings and stores. Their goal was to create something more pedestrian friendly, engaging and less monotonous. At the time, the all white exterior was seen as being just the opposite.
Time has obviously proven them wrong. The original was far superior, and I don't the changes have fostered greater pedestrian engagement.
As for Nordstrom's I believe they're aiming for a sense of exclusivity by having a large wall and relatively small entrance. Something brighter and more engaging would benefit the mall overall, but I guess they're going to do what they feel best ties into their brand.