This factory implements the closure-based private state pattern: 1) It creates a private state container inaccessible from outside, 2) The returned object only exposes getter methods for accessing private data, 3) No direct modification of private properties is possible, 4) Each employee instance gets its own independent private state, 5) This achieves true encapsulation without classes or symbols, 6) This pattern is often used to create objects with controlled access to internal state.