The documentation appears to suggest that TWTRComposer does not require a logged in session, but the TWTRComposerViewController does.
https://dev.twitter.com/twitterkit/ios/compose-tweets
Previous SDK versions 2.x.x did not require the user to login to twitter to compose a tweet when using TWTRComposer.
Is there a way to compose a tweet without asking the user to login?
This behaviour is also different to the Android SDK which does not require a logged in session.