Your point? I cannot see what this has to do with attempting to
classify applications; it is orthogonal to what I wrote.
If you where to render a geometry (say a TV) with a picture on it (say obtained by <video>) and you do not specify unpack flip y then your UV coordinates need to go from top/left 0,0 in order to get a correct display. Now if you render that <video> using the same semantic (0,0 top/left) into an FBO (say for some postprocess) and then texture your TV geometry with that, your picture is upside down because in the framebuffer attached texture top/left is 0,1 in UV.