"from an unprotected template" do you even read?
stop trying to find some random internet page to justify yourself, have you ever seen a biometric implementation? I have.
> there are studies showing that the hash could be reversible, that is, it could be possible to obtain the original biometric pattern, especially if the secret of the key used to generate the hash is violated
So yes, there are secret keys involved (which the user has no control over), and no, I've never read through the code of a biometric implementation, but ultimately the space of possible values that someone's face or finger could reliably display is much smaller than even MD5, so it can be brute-forced.
If you have some non-random internet page to justify yourself, and show how much entropy is contained in a biometric hash, and how resistant to cracking that hash is, and how well secured those secret keys are, then I'd be happy to learn more.
[0] https://edps.europa.eu/sites/edp/files/publication/joint_pap...