There's an ongoing initiative to remove the AppMenu from the top bar and replace it with a primary hamburger menu.
Applications which use in-window navigation should only show the primary menu on the top-level view (typically the main view that is shown when the app is launched).
Since we only have one non-top-level view (individual Album view), we use this globally. This would be in line with other buttons keeping the same place in the album view that they have in the top-level view. This also works because there aren't view-specific actions for the individual Album view.
Secondary menus are optional and only need to be used if there are enough controls to require a menu.
Based on this and the reasons mentioned above, we shouldn't need to use this at all.