Want to thank Jacob for the actual AWD rear suspension pictures. I can see no difference bar the beam itself in the double photos of FWD and AWD provided by Mazda - if the springs have been moved, it is not shown, as they line up exactly the same way relative to the holes in the rear wheel guard, etc.
And the CX-3 is indeed based on the Mazda2. Mr. Yarkony simply got it wrong in the original article saying it was based on the 3. The floor pan is thicker on this CX-3 and incorporates the rear crash structure by itself, rather than with added pieces as on 3 and CX-5. The thicker floorpan's why it's quieter.
Torsion beam rear suspension exactly to this layout featured on the original Golf 40 years ago, coil springs and all. That car had an additional sway bar too on some models. This Mazda version seems to be an almost exact copy of the current Fiat 500, but as it's so simple a design, they all look pretty much the same these days.