The main menue is displayed in fullscreen and makes the impression of being an extra page.
One could therefor try to exit the menue via the back button of one's phone, what does not work.

If the main menue would be presentetd as side draw menue, it would be clear that it is infact a menue and not a page.

In order to make all the buttons fit in the side draw menue one should just have one-two buttons per line. (this would also resolve the task T3074 [mobile] Strange kind of feature arrangement in main menu)