But they do? Works fine for me on GitHub, which is the place I most often use it, but also other places if I needed them on my phone.
Not only that, they also both provide the same underlying technology to 3rd party apps, because the core trick in WebAuthn uses a cryptographic hash of a DNS name, so if we put say a UUID minted by your app store in where the DNS name goes we get the same functionality, (logically collisions can happen, but they're astronomically unlikely) but customised for each phone vendor & each app.
So e.g. I tap the icon for the NHS app on my Pixel 6, it starts up to where it would want me to do nonsense with passwords and so on but nope, hold my thumb against the screen, biometric match inside the phone, therefore this is my phone, it has a FIDO-style proof that this phone, which enrolled via the laborious process with passwords and SMS and whatever, is mine and it says this is me. Now I can order routine prescription re-fills, they go in a queue, my doctor says yeah, tialaramex doesn't need to re-check those blood levels until summer, prescription approved, done.
WebAuthn is an open standard and is available on all platforms and devices. There's not much reason to mention iOS, Apple's implementation of the standard is nothing unique.
Not only that, they also both provide the same underlying technology to 3rd party apps, because the core trick in WebAuthn uses a cryptographic hash of a DNS name, so if we put say a UUID minted by your app store in where the DNS name goes we get the same functionality, (logically collisions can happen, but they're astronomically unlikely) but customised for each phone vendor & each app.
So e.g. I tap the icon for the NHS app on my Pixel 6, it starts up to where it would want me to do nonsense with passwords and so on but nope, hold my thumb against the screen, biometric match inside the phone, therefore this is my phone, it has a FIDO-style proof that this phone, which enrolled via the laborious process with passwords and SMS and whatever, is mine and it says this is me. Now I can order routine prescription re-fills, they go in a queue, my doctor says yeah, tialaramex doesn't need to re-check those blood levels until summer, prescription approved, done.