Great. Thanks all. So it sounds like a function of minimum focusing distance more than anything else.
Sort of. True only if you are comparing lenses of the same focal length. A long lens will provide greater "magnification" at the same distance as a mid length lens.
I think there is an industry "standard" that allows any lens with a 1:4 magnification to be advertised as a macro lens. It seems rare to find a zoom that says it has better than 1:4.