cut and paste the above to a IE address bar will take one directly an IDPs login page. It will not show the organizational ID picker.
When in the WPF sample with ADAL (see MSDN) develops the same URI, the ID picker shows. This is despite having adopted the counsel of the sample (to prevalidated RP domains, learn their 'specific domain' IDP and confirm it aligns with that/those that the fit the client's trust model - about which IDPs it is willing to entrust to challenge users, "audit" them, [not] enable spying on them, etc etc)
I dont have a clear mental model when custom semantics are to be respected, when custom semantics are imposed (even though one gives a specific domain), and when the custom domain is respected. It seems to depend on the environments - browsers, store apps, WPF...