Experiment arms finer than location error

Assigning experiment arms at a cell grain finer than the delivery channel's location error radius misplaces households across arms. With shared error the misassignment is non-differential (attenuates lift toward null, a power cost); when arms differ in IP-resolvability — multi-family share, carrier NAT, fixed-wireless penetration — the error becomes differential and biases the estimate, not just weakens it.