OK I see.
With the Twitter app installed, using an account, the login flow sends us to the Twitter app, shows a confirmation dialog for the app at apps.twitter.com, then sends us back to our app. Not too bad. Previously there was never any details concerning the app at apps.twitter.com.
Still I think most people would prefer to use the system accounts. Me included. I really hate to input user/pw suddenly, 99% of users already entered those into iOS settings. On the whole I guess people will engage less with Twitter through 3rd party iOS apps from this because of the added friction. The latest 2.x line of TwitterKit worked very seemlessly.
If the reason for all of this is to show the details (permissions etc) of the apps.twitter.com app, you could as well bake that confirmation screen into the TwitterKit framework and allow us to show it on top of the current view controller?