It's effective for people with ADHD because ADHD makes it difficult to see that first step, preventing one from getting started[2]. Visualizing the steps helps build the ladder over the wall of awful that you need to climb to start Doing The Thing.
Telling yourself that you're not going to Do The Thing now, you're just going to _______ (think about the steps, just do the first step, etc) is also a very effective ADHD srategy: you're fooling your brain into doing what you want to do by taking the pressure off. The whole task seems insurmountable, but finding that first thing that's relevant to the task and seems easy is the trick to getting started — and once you get started, there's a decent chance you'll go until it's done.
These techniques are helpful for everyone, but they're doubly important for people with ADHD, and are frequently discussed in the community.
And yes, it's absolutely work even if it doesn't feel that way. To the outside world, you might be sitting there being stuck. In reality, you're climbing that wall.
Often when I actually do the thing, I realize it is harder or feels worse than I was consciously feeling. It makes me think, "Oh yeah, no wonder I was putting this off. This is hard."
An example of this is decluttering, which sounds easy but in reality involves making a lot of difficult, often emotional decisions (i.e. coming to terms with the fact that I'm not actually going to use something any time soon so it would be better to get rid of it than keep it hanging around taking up space).
I'm in the middle of a big declutter at the moment (actually not only decluttering but moving rooms around) so I can totally relate. Remembering things you once wanted to do but ended up on a shelf, can really suck, especially if the conclusion is "actually I'm never going to do it, so might as well donate it".
"I won't do X now, but I will stop browsing and walk around the block while thinking of X."
"I won't do X now, but I'll sketch some ideas about X on paper while I have a coffee or snack."
This helps for those situations in which I'm procrastinating due to a realized or unrealized ambiguity of a given task. If I'm slacking because I don't know how to do something, it gives me the questions that I need to go find answers to. Googling around for answers or pinging a coworker is way easier than actually doing the work, and thus I can 'get the ball rolling' so to speak.
Even if I still procrastinate a bit afterwards, the tasks seem much more manageable as I already 'know' what needs to be done, letting ideas stew at this point. Usually after a snack or bathroom break, I'll come back and just crank out the work (or at least start!) because I'm so sick of thinking about how simple that first step actually is, again, because the details are already worked out in my head.
In a literal sense, this is 'work/working', but it never feels like it, and that's part of the key for me to overcome it. It's just thinking, right?