The "conditional" is carrying a lot of weight here. The developer needs to know what to do. For example, in my GTK application I had to learn how to identify a menu as the "primary" menu, so that the framework will automatically bind it to the well-known shortcut.
<object class="GtkMenuButton">
<property name="primary">true</property>
This is easy to omit and then you will never know about the automation.Then, you can go into a different discussion. How does the framework guide you to the correct functionality? Does it force you to include a primary menu? Does it check that if you have at least one menu, then one should be primary? What if the developer creates an unorthodox menu by creating a simple button that opens a popup with a list of buttons?