Julie,
You are correct. You also put a whole lot of thought into your delegating decision in terms of to whom to delegate. Who has the necessary skill sets, who can benefit professionally from this assignment, etc. The follow up that you mentioned is key, too. Checking to see if the employee has questions and if they are progressing appropriately is important. You still, however, maintain ultimate responsibility for the successful completion of the assignment.
Dumping is simply of way of getting it off your desk with no thought given to the benefits it might have on the recipient of the assignment.
Pat