They do upload in the background, but they don't notice new photos while being in the background.
You need to start the app and only then they will notice the new photos. (my life is miserable because my wife has iPhone and I have to deal with strange limits on iOS).
The iPhone does have a search for apps. Plus they now also will group your apps into categories on the last screen.
And apps like Google Photos on the iPhone do upload photos in the background.