By being given an iPhone/iPad and clicking around, you wouldn't even learn about what a filesystem is, let alone about anything else in terms of how your device works.

On a PC, just by being bored you can learn quite a bit about how the OS works; you can access devtools from a browser; you can learn tons and tons by trying to get some old/obscure game to work; you can google "how to make a game" which would probably lead you to a download page for python, which you could install and start writing some scripts; you could easily stumble upon Blender and some tutorials and start 3D modelling.