I would say this example is exactly the reason that DA defines "project" as he does. We are not likely to forget the big projects in our life, but these small multi-step processes are the kind of thing that can slip through the cracks without a placeholder. Faced with this situation I would immediately enter "submit form re XYZ" on my project list, with a due date if applicable, then look at whether it deserves to be on my current next action lists. If it is urgent, I may, in fact, complete the project in one sitting the very same day, making the entry on the project list seem a little excessive. But if it is not urgent, or for some reason I only complete part of it and then forget to note the next step on my next action lists, the entry on my project list is how I get reminded to finish it. I see that entry during my next review of my project list and think - oh yeah! Gotta send in that form!
It's funny you should mention this, because I do the exact same as you and also just the opposite. I also immediately enter those tiny little mini projects, but not on my project list, but rather on my next action list, with the deadline next to it. The rest goes the same as in your case. Either I complete almost immediately, either I do it later, and the fact that it's on my NA-list prevents me from forgetting it. So my placeholder is in my NA list for those mini projects, not in my project list.