The instructions you linked are for SAML applications.
For OIDC applications you can use,
Initiate login URI (if the Org is OIE)
IdP routing rules setup specifically for this application
In the /authorize call your application generates and redirects a browser to, add the option prompt=none as a query param. If a users browser does not already have an Okta session, the browser would redirect to your apps redirect_uri with an error message instead of landing on the Okta hosted login page . Your app could handle this by presenting the login screen.