Yes, as you indicate, Jetpack seems to set scale=0" on all images (and also sets the intended width= and height= properties as intended on the post image insertion definition itself). But it appears this scale="0" may be what causes conflict with other plugins (notably Retina 2x).
The conflict I found was that Retina 2X would then change it to scale="2" but also adjust the width= and height= property values to be much smaller than the original values, thus "hard-wiring" the image size and causing it to not properly adjust on an ipad when turning devices from portrait to landscape. Since the width and height were hardwired for the portrait orientation, it would look small on landscape.
However the fix you provided above eliminates the scale="0" altogether, removing conflict with the Retina 2x, which will now leave the width/height at the original values and thus not cause display issues on portrait/landscape re-orientation.
Thank again for your suggested fix.