That is one of the great things about mobile devices. They do strip away all of the extra things that can steal your focus. I was also surprised by the findings of that study. I would have thought just as you did, that comprehension would drop on tablets and e-readers. I'm not sure why I thought that though. I own a Kindle and I wouldn't say that I have understood less any of the books that I have read on it as compared to the physical books that I have read. I wonder why that perception is there? Is it just because print texts are our preference? As a teacher though, I'm glad to know that there is no difference in comprehension levels.
Yes, that is true. Many tablets don't have the popups and tool bars like reading online. So therefore there is not as much distraction with those devices.