First of all, based on this review it sounds like the app pauses the export after 10 mins and then simply continues where it left off when the app is reopened:
Second, the app hasn't been updated in 2 yrs and has terrible reviews in the app store.
Again, no. I have had it render for over an hour in the background.
You also ignored the fact that iMovie does the same thing. And it is an app store app--not a preinstalled app, such as Mail (which has had background operation since the iPhone 1 was first released).
I honestly don't understand the relevance of the "terrible reviews" comment. It has 3.5 overal rating. More good than bad. But again, irrelevant to the point at hand.
Michael