The way it's currently implemented, when I view the list of tasks I'm seeing a list of single tasks and the Projects but not the Project Sub-Tasks. When I'm looking at a set of tasks under a context, often I don't see the actual sub-task but I'm seeing the Project heading. In order to see the actual task I have to tap on the Project heading. This makes a quick scan of tasks impossible.
For instance, if I'm out on errands and filter with the Errands context, I might have 10 projects listed that I would need to tap one-at-a-time in order to get to the actual tasks at hand. I don't know what the solution would be, but the current arrangement is just not working.
I know some people create a separate List for Projects, I put all the current items on one list and use a Project context to view all the projects at once, but I don't think this makes a difference with the view of individual tasks.
As it is now, it appears that Projects and Tasks are placed on the same "level", with Project Sub-Tasks on a lower level:
IMHO the Tasks and Sub-Tasks should be at the same level, with Projects at a level above: