Imagine if every time you resized a window on your PC, the window got killed and restarted, and you see why bugs like that arise.
It'd be one thing if it was when the app is backgrounded, but no, even if you have one app running on your entire device, the UI be torn down.
It's insanity that in 2022 a major operating system is still doing that, and yet here we are with no end in sight.
But you know what? Maybe instead we should discourage people from clumsily trying to push their pet agenda the moment their favorite sports team (erm excuse me, Operating System) is painted in a poor light.
But we can't all get what we want can we?
This is something you learn very quickly once you start building Android applications -- or, at least, I did when I started back in 2011 (I haven't done much Android dev in the past decade since then). While I do think this behavior is a pretty terrible default behavior for the underlying UI framework, it's pretty bad that the AndFTP developers have not fixed this bug in their application -- and yes, it is a bug in their application.
The UI development paradigm has changed quite a bit over the life of Android, making "Fragments" more popular to use in some quarters than "Activities" as the "unit of UI screen" (though Fragments are still underpinned by Activities), but I believe the fundamental issue is still there: if you don't explicitly handle rotation properly, and store state in your Activity, it will get destroyed whenever the screen is rotated.