iPad on maximum brightness is what they were using. They sure buried it!

That would be close to painful and certainly very unpleasant in a dim room at night.. WTH were the study authors thinking?

The iPad won't even do that without the user manually setting it up to do that, and almost no one is going to find it comfortable.

It seems more like they were trying to set the conditions to get the result they desired. They could have shined an LED flashlight into the user's eyes and gotten the same result.