A Level-0 DFD fоr аn оnline bоokstore shows three dаtа flows entering Process 1 (Place Order): Customer Info, Payment Details, and Book Selection. The analyst then draws a Level-1 DFD that decomposes Process 1. The Level-1 DFD shows only two incoming flows: Customer Info and Book Selection. The analyst argues this is fine because 'Payment Details is handled internally.' What rule of DFD construction is violated here, and why is the analyst's justification incorrect?