Oh, so now Eliza Dushku is getting sick too, that should help move matters!
Just to repeat myself:
- visual motion can induce motion sickness
- APPARENT )perceived, illusionary) visual motion (e.g. http://www.psy.ritsumei.ac.jp/~akitaoka/looserotsnakes2.jpg or https://www.google.fr/search?q=rotating+snakes&es_sm=93&source=lnms&tbm=isch&sa= X&ei=YzBFUoGPMaGg0QXz9YCADA&ved=0CAkQ_AUoAQ&biw=1026&bih=664&dpr=1) can induce motion sickness
- making certain head movements while watching something that can make you think you're moving can induce motion sickness (coriolis effect; https://www.google.fr/search?q=coriolis+effect+motion+sickness&es_sm=93&source=l nms&sa=X&ei=QzFFUry7Jcii0QXT0YHgCw&ved=0CAgQ_AUoAA&biw=1026&bih=664&dpr=1)
- even without apparent motion, image content can be stressful/obnoxious enough to provoke migraines in susceptible people. There is a neurological link between migraine and motion sickness (not yet well understood AFAIK), and of course migraine symptomes can include nausea. As to the image content in question, think things like the rotating snakes image linked to above: "aggressive" colours and colour contrasts in sufficient amounts. On computer screens one can add the moiré effects ("instability") caused by interference between image detail and the display (pixel) raster. The simple act of increasing display resolution to a point where the display raster is finer than the theoretical resolution of human vision (as measured by foveal photoreceptor density, for instance) does NOT mean that said interference can be disregarded. An inaudible high frequency sound can create perceptible interference ("beats") in audible sound, and the same can happen in vision ... and we have somehting called hyperacuity allowing us to detect things that are theoretically too small to be seen.
In short, I don't think one can explain the symptoms people are having to a single feature of iOS7. It's a combination of things, most likely quite personal (for some it's mostly the colours, for some the zooming, for some the parallax, etc), but all leading to a common set of symptoms that most researchers think are a way the brain has of telling us something is amiss with our sensory perception or the way we process that information.
In this case it's really comparable to a novel interface that generates almost instant and very powerful RSI (another of those medical conditions that took a while to be taken seriously).
As to quality control/testing that allowed this to get through ... I fear it's more likely it was pushed through, maybe even for as incredible reason that a British aristocrat with a design degree and reputation cannot be wrong ... even (or especially?) if he deviates so humongously from his usual pure and self-effacing designs. It's beyond understanding to me that there is no "graphite" theme to chose from, like there has always been in OS X, for adult users having outgrown their taste for colour candy.
Oh, and to the person who thought that it could be easier to implement a duration/speedcontrol on the animation effect rather than a switch to turn them off: I don't think so. For one thing, setting the duration to zero is one way to turn them off, but if they're implemented as a (device-specific) fixed series of "slides" it'd be harder to give (fine) control over the duration rather than just skip everything all together.