I believe this relates to the listpicker button and this block and the gotFocus block are a hangover from when cursor/pointer type devices were used for AppInventor. There is similar for a normal button. Just do not use these blocks.
A quote from Evan Patton on the button blocks:
The original use of the GotFocus/LostFocus events were when Android phones had trackballs to navigate the UI. Focus would move when you moved the trackball highlight over a component (e.g., button). In the days of touch screens and no trackballs, the events still exist but are likely only triggered in limited circumstances (computer emulators with mouse being one, accessibility focus is another).