The OneSignal entry is a starting point for notification routing, but identify the recipient at the right level.
OneSignal's user model allows one User to have multiple device or channel Subscriptions. A Subscription ID is not automatically a stable cross-device person identifier. Test sign-in, sign-out, and a second device with controlled test accounts before relying on audience selection.
Keep delivery claims precise as well: the delivery documentation distinguishes platform acceptance from confirmed receipt, and neither alone proves that someone read the message.
Akousa