If true, perhaps it's like the much-maligned (yet brilliant!) 24-70 F/4 IS macro mode, in which the macro only works on the 70mm end?
Stupid question that I still want an answer to: Is it possible to have a 1x magnification at more than one focal length in the same lens?
Well, they could in theory have a build-in adjustable extension tube that automatically adjusts when in Macro to maintain 1:1 at all focal lengths. Of course, it'd be way cooler if it was free to be at any position so we could get >1:1 magnification at the shorter focal lengths if we wanted. Being cynical, that wouldn't happen because Canon would want another $$$ to 'enable' that feature on a lens because then it's >1:1 so they can charge more.
Even if they could do this, what would the IQ be? Macro tend to be incredibly sharp - could a macro zoom meet this hurdle?
I would like to see a 180-200 macro with Tilt capabilities (don't need shift). That would help with DOF which is very narrow at magnification