> uses biometrics to validate the number
Biometrics can be trusted only as far as one can trust the source of the biometric info being provided. If you're getting biometric info as digital images, you'd have to be sure the images came directly from the person, only for this validation, and (if you want to use this validation for authentication) voluntarily.
The first two can be achieved only if the biometrics are given straight to the government's biometric verification authority, instead of whatever service needs to verify your id taking them and passing them on to the government. The latter is like giving your Facebook username and password to a third-party just so they can verify your Facebook account, the former is like an SSO service.
I have not seen a single SSO-like implementation of biometric Aadhaar verification in India.
And, of course, the third requirement cannot be fulfilled; biometrics are not passwords.