If this flag is set the system will regard views that are not important for accessibility in addition to the ones that are important for accessibility. That is, views that are marked as not important for accessibility via Android.Views.View.ImportantForAccessibilityNo or Android.Views.View.ImportantForAccessibilityNoHideDescendants and views that are marked as potentially important for accessibility via Android.Views.View.ImportantForAccessibilityAuto for which the system has determined that are not important for accessibility, are reported while querying the window content and also the accessibility service will receive accessibility events from them.

Note: For accessibility services targeting API version NoType:android/os/Build$VERSION_CODES;Href=../../../reference/android/os/Build.VERSION_CODES.html#JELLY_BEAN or higher this flag has to be explicitly set for the system to regard views that are not important for accessibility. For accessibility services targeting API version lower than NoType:android/os/Build$VERSION_CODES;Href=../../../reference/android/os/Build.VERSION_CODES.html#JELLY_BEAN this flag is ignored and all views are regarded for accessibility purposes.

Usually views not important for accessibility are layout managers that do not react to user actions, do not draw any content, and do not have any special semantics in the context of the screen content. For example, a three by three grid can be implemented as three horizontal linear layouts and one vertical, or three vertical linear layouts and one horizontal, or one grid layout, etc. In this context the actual layout mangers used to achieve the grid configuration are not important, rather it is important that there are nine evenly distributed elements.

[Android Documentation]