OK - yes, technically an injury is any physical damage to the body, although I'm not sure about just impact, isn't a twisted knee also an injury?
Also, the impact on the bottom of your feet when you jump two foot in the air would also kill you if applied to the ase of the skull or neck. It doesn't seem an apropriate comparison.
As usual, the discussion over the poll question turns into a question of definition (which is good, as it means usually we all agree with each other). As almost everyone get a few bruises when they learn to roll, I didn't count this level of damage as an 'injury' in the context of the poll question (a 99% yes answer isn't so useful).
Don't forget, by your definition EVERY roll causes an injury. We're not usually aware of it, until we've done 50 or so, but its there. Ukemi is just intrinsicaly not a healthy activity.