Hi,
Thanks for reaching out. In the scenarios above when you come to Adobe it would redirect to your companies IDP SSO sign in page. Once you are signed in, it would redirect back to Adobe. If you have already signed in via corporate mail one of two things can happen:
1. You are directed to Adobe because your system recognizes you as logged in.
2. You are directed to a sign in page, then redirected from SSO to Adobe once it recognizes you have already authenticated.
Let me know if you have any additional questions on this.
Best,
Tacia