This Add-on disables the display of emojis in smilie menu on Android and iOS.
Showing emojis in smilie menu is useful on devices that usually do not have native support for selecting emojis (eg. desktop devices).
It is less useful though on mobile devices powered by Android or iOS on the other hand as they commonly have native input support for smilies via virtual keyboard - which is often easier to use (as users are used to that) and gives better performance (especially with slow/bad network).
This Add-on allows to have the best of both options - emojis are being displayed for easy selection on non-mobile OS but are not being displayed on dvecies running Android or iOS.