Why does it not exist via @AppStorage

2 versions 1 works 1 doesn't. UIViewRepresentable to show a PDF

@AppStorage(DefaultsKey.userActiveBook.rawValue) var activeBook : URL = Bundle.main.url(forResource: "BookPlaceHolder", withExtension: "pdf")!

func makeUIView(context: Context) -> PDFView {
do {
  let pdfData = try Data(contentsOf: activeBook)
            pdfView.document = PDFDocument(data: pdfData) //<---- is nil
            ...
}
 catch let Error {
       print(Error)
        }


}

fails with

Error Domain=NSCocoaErrorDomain Code=260 "The file “BookPlaceHolder.pdf” couldn’t be opened because there is no such file."

func makeUIView(context: Context) -> PDFView {
do {
  let pdfData = try Data(contentsOf: Bundle.main.url(forResource: "BookPlaceHolder", withExtension: "pdf")!)
            pdfView.document = PDFDocument(data: pdfData)
            ...
}
 catch let Error {
       print(Error)
        }


}

Works perfectly. What is it with using @AppStorage to access the exact same URL causing the discrepancies ?