Old Android menu as a bug on Google Pixel 2
Google Pixel 2 and Pixel 2 XL users will get a new update soon, for sure. Secret menu is discovered in those devices, which you can acces simply by tapping at the lower right part of the screen, you will feel haptic feedback, and that same menu will open, which has been used in Samsung Galaxy Nexus, on Android Ice Cream Sandwich.
Google confirmed that this is not additional feature, it's a bug in the system. They said that if you want to see it, you better do it soon, untill it dissapears forever.