The 'alert arrives before final settlement' point is the part that matters most for anyone building on top of NIP — your ledger can show a debit and the recipient's app can show a credit alert while the underlying net settlement between banks at CBN hasn't happened yet, so treating the alert as proof of finality instead of the batch settlement is exactly how reversal edge cases get mishandled. It's the same instant-notify-vs-deferred-settle gap we deal with reconciling PSP webhooks against acquirer settlement files — the notification and the money moving are two different events with two different failure modes.