This happens because data stored by the iOS app in device’s secure Keychain does not get cleared automatically after the app is uninstalled at the end of the test session. However this is not a security issue because the app’s keychain data is not available to any other app, and cannot be retrieved, changed, or deleted by any other entity apart from the app itself.
In order to automatically clear keychain data at the end of every Appium session, you can pass ios_keychain_support parameter during the app-upload stage on BrowserStack. Refer to this page for further details.
