It a Designer thing. Postman does not seem to show a Basic auth dialog. So the Designer will automatically sign you in as `Developer`. You will not see such behaviour with a real engine.
But you could specify pro-actively a user to log in with postman by setting secure auth headers:
![alt text][1]
Another thing that could be confusing is the cookie store that knows the attached JSESSONID once you had a successfully authenticated session. You may clean it up manually to switch the user
![alt text][2]
[1]: https://answers.axonivy.com/upfiles/postmainAuthHeaders.pnghttps://answers.axonivy.com/upfiles/postmainAuthHeaders.png
[2]: https://answers.axonivy.com/upfiles/postmanCookies.png
