Thank you for your help.
Which demo app are you using? Could you share it?
But the scenario is actually same.
Try to login by logInWithCompletion from my developing app using my protected account, and then fetch my tweet by statuses/show.json. But the tweet is posted from another app using my protected account.
According to the behavior, I guess I can’t get proper authToken because I can only access to public tweets.
Originally this issue was happening on TwitterKit 2.8.1. And then updated to TwitterKit 3.1.1, still happening.
When I investigated this on TwitterKit 2.8.1, tried logInWithMethods with TWTRLoginMethodWebBased but still happening.