Why does a wall "move" when I change expirations?

The expiration filter is cumulative. Selecting an expiry includes it and everything nearer, so you're adding books, not switching between them. As you widen the selection, the biggest concentration can land on a different strike. The wall didn't move; the book you're summing changed.

The Matrix narrows with your selection too, because its columns are the selection. Price-action levels (prior day, volume profile, pivots) ignore the expiration filter entirely.