Is the solution presented in the blog to utilize a cookie to determine if someone is a prospective user versus already a user not an acceptable compromise? It

Is the solution presented in the blog to utilize a cookie to determine if someone is a prospective user versus already a user not an acceptable compromise? It seems rather straightforward to me, from their example, to de-emphasize the "Sign Up" button and prioritize the "Sign In" button for someone who already has an account.