SAML SSO Configuration in service Portal - mixed Mode


After configuring SAML SSO, the only difference I am seeing is login page, earlier we were using Service portal login page but now we are using ADLS login page, in both the place user has to type his username & Password

we are expecting SSO login with typing username & Password i.e when user Opens the URL, it should take AD credentials to login

we opened a support case to take assistance from support team but they confirmed that is the actual behavior,  even in the below URL. I only see the details of logging in from ADLS Page.

Can someone add more light on expected behavior and steps/Document.

Service Portal = 2018.08
SM Application = Codeless
SM App version = 9.52.0011
SM Web Client = 9.52.202