I'd say for the purposes of this article anything that is required in order to have done the thing is "doing the thing".

If you need to read something to get the thing done you are doing the thing. If you already know everything to get started but still read another article you are procrastinating. If you need to sand this part to do a good job painting it, then you are doing the thing. If you just continue sanding with no benefit you are no longer doing the thing, you are now just delaying the next step

Additionally, a lot of people will describe doing completely unrelated things as "(mentally) preparing to do the thing."

I catch myself doing this. I will put off writing a job requisition by spending time on code. I will tell myself, "ugh, I'm just not in the right mental state to write a job req right now. Let me focus on some code until I'm ready." Which never works. I end up getting into a code flow state and that's all I work on for the rest of the day, or until I get interrupted by a meeting.

And then I get back from the meeting and say, "I got interrupted, I should just finish what I started and then I'll write the job reqs." And that never happens. I always pick up yet another coding task instead.

The only way I am ever able to get through admin paperwork is to just admit to myself I hate it but it has to get done, it has to get done right now, no amount of procrastiworking is going to make me stop hating it, so I should just get it over with so it's not sitting like a lead weight in the back of my head. And then when 5pm rolls around, I won't hate myself for letting yet another day go by without having the job reqs written.

But right now it's the weekend.