Interesting stuff but I tried adding "waitfor delay '00:00:01';" to each of the sample work SQL tasks in the OnePackageMethod (before the update statement). That way you can see what is happening because the work takes longer. On my workstation I observed that none of the tasks executed concurrently. They each execute in turn. Maybe on a server it would behave differently?
I've seen wildly varying performance on different machines, and while SSIS will try to run multiple items if the package is built to do that it can't always do it, on a single processor machine (no hyperthreading either) I doubt it will do it. On a server and even a laptop with multiple cores and a couple GB of memory you will see it thread..
Thanks for reading..