What is verification wall?
A verification wall is the point in a sign-in where the site demands something beyond the password. Twin distinguishes the kinds because they have different answers: an emailed or texted code can be fetched automatically when an inbox or phone number is connected, while an authenticator code or a phone approval is something only a person holds.
Why it matters
Most automation treats every second factor as a failure. Splitting the fetchable ones from the human ones is what turns "cannot automate anything with 2FA" into "automates everything except the parts that genuinely need you".