How different are VNRecognizedTextObservations (returned by VNRecognizeTextRequest) to the RecognizedItem array returned by DataScannerViewController? Do they have the same information in them? Also, is the DataScannerViewController using the same VNRecognizeTextRequest (with revision3) in the background to process the results?
RecognizedItem contains a lot of the same information, like transcript, corners (RecognizedItem's are in view coordinates, however)... and RecognizedItem exposes the related Vision observation.
RecognizedItem however learns over time so the longer we see a text group, the more accurate the transcript will be. The Vision observation that is exposed, it is really just based on the last frame processed.
I cannot state which revision it uses, if any (sorry to be vague), but DataScanner supports the same languages as VNRecognizeTextRequest.