The layer on top, and the pitch

What @expo/ui adds on top of your primitive

You've built the reusable floor: ExpoSwiftUI.View primitives, Children() composition, controlled values. @expo/ui's value-add on top is a modifiers system — a modifiers prop carrying a list of SwiftUI-style modifiers (padding, frame, background, onTapGesture) that get applied to the native view.

That's why @expo/ui's props extend UIBaseViewProps and the TS binding wraps events with createViewModifierEventListener — event-based modifiers like onTapGesture and onAppear need their callbacks routed through the same EventDispatcher machinery you already know.

In an interview, say: "@expo/ui = SwiftUI/Compose-native primitives + a Children() composition model + a modifiers system layered on the base view props. I built the first two on the public primitive; the modifiers layer is its internal UIBaseViewProps/ModifierRegistry plumbing."