I've spent over 2,000 hours on YouTube this year alone and am in the target demographic of this study. I watch a lot of videos in the background while I work, commute, or just chill, to keep myself stimulated.
Although not all of the content I watch is necessarily educational, a grand majority of it is. Whenever there's a science video in my feed, I'll probably click it. I'm subscribed to Veritasum, TED, Vox, No Boilerplate, etc.
Usually the plan is to go to China and then flee to a friendlier country. There are also people in China who work with North Koreans to help them defect.
It's a limitation imposed by Apple, so you won't find anything that can sync as seamlessly as iCloud. Apps can only sync for up to 60s in the background when receiving a wake-up notification from the server.
Public Mobile ftw