Okta is more of a SAML/OpenID Connect thing with built-in multi factor authentication than a replacement for WebAuthn, though. Okta could embrace WebAuthn Platform Authenticator as one of their authenticating factor if user is unwilling to install an app, but a website isn't expected to use Okta as a second factor in their authentication flow.

OP is referring to how you already can sign in to Okta as a website, not as an authentication mechanism. You can create a sign in flow that goes like so:

username -> password -> [ WebAuthn | Okta Verify Push ]

This approach can be used on any website, just with a regular TOTP code in place of the proprietary Okta Verify Push.

Ah I didn't know you could do the Okta push without using their whole SSO suite. Thank you! I guess in this scenario Okta acts more like Authy proprietary OTP thing then.