Converting an image to a template requires similar images to result in similar templates. That's usually the opposite of what you want from a hash. There is a concept of "biometric hashing" that would accomplish the one-way claim, but it's theoretically hard and as far as I know none have hit the accuracy levels to make the biometric part feasible for a large scale systems.[1]
The real claim biometrics vendors tend to make if you push them is that you can't reconstruct a photo-realistic image of the face / finger / iris from the template. Which is generally not a true claim either, but at least would require some work with generative tech. And a photorealistic image that generates the same template is likely to look a lot like the actual person.
Source - 10 years of consulting in biometrics for government, academia, and industry, including spoofing and vulnerability assessments. Most people in the industry don't know what they are talking about and just repeat marketing claims.
[1]https://www.cse.unr.edu/~bebis/CS790Q/PaperPresentations/Bio...