double tap on this button let you switch between 2 most recent apps? is this standard or something wrong with my button?
That is a new "gesture" that works like you found.
Also, depending on the apps, pressing and hold on it can divide the screen in half with two different apps. I'm not yet proficient so I don't have the "presses/touches" necessary to execute it. And, not all apps can share the screen with another.
double tap on this button let you switch between 2 most recent apps? is this standard or something wrong with my button?
It's an Android feature and really useful if you accidentally close a window by hitting the center buttonhole tap of the square and your screen will reappear!