My point is the difference is a difference of terminology not in functionality. A zoom system is one that can achieve multiple focal lengths with the same setup, and in that sense the iPhone 7 plus has a 'discrete' zoom, just like for example, microscopes, or telescopes with different magnifications, or leica's tri-Elmar lenses. (Leica doesn't call them zooms because in the world of Leica primes are the standard, but I don't see why you wouldn't.)

If you define zoom as the physical action of sliding a piece of glass to achieve different focal lengths in a lens, then a digital zoom, by that definition is also not a zoom.

Now, the iPhone is not using a teleconverter, which is something that is added to the lens, but a different lens plus sensor alltogether to create the effect of a zoomed image. And this is the point where the old definitions break down; is a camera the sensor or is a camera the device that creates the picture? I think it is the latter, and in that sense I think iPhone 7 plus does have a 'discrete' zoom.