That's not how it works. The process of reading your retina / fingerprint is error prone. You can't take hash out of error-prone data blob!
My understanding is that matching the pre-saved template against a fresh scan is a process similar to measuring Levenshtein distance. There is some threshold, and sample with smaller error are accepted. This does imply that the iphone has somewhere stored your _unencrypted_, _unhashed_ template of your fingerprint.
But this is not my area of expertise. Perhaps a subject matter expert can comment.
My understanding is that matching the pre-saved template against a fresh scan is a process similar to measuring Levenshtein distance. There is some threshold, and sample with smaller error are accepted. This does imply that the iphone has somewhere stored your _unencrypted_, _unhashed_ template of your fingerprint.
But this is not my area of expertise. Perhaps a subject matter expert can comment.