This is intentional. You now have the following options available:
The option to log out AND send client feedback by calling a Java action in a Microflow. We did not include this option as a Microflow activity because you would only use it once in every application, but you can create a simple Java action that logs out and sends logout feedback to the client so that the client knows it should reset itself. This means that you can put your logout button anywhere where you would normally be able to put a microflow, including in your navigation. It removes the need for a special case 'menu' widget that had this button and username information before.
The java docs have not been updated yet or I would link you to them, but to send the logout feedback to the client, use the com.mendix.webui.FeedbackHelper.addLogoutFeedback() method. For actually logging out you can use Core.logout()