And now we have a whole post about not doing the thing, which is also not doing the thing.

In order to determine if something is or is not "doing the thing" you must first know what "the thing" is. If it's writing your thoughts on your blog, then this is indeed doing the thing.

Not doing the thing would be: planning to write a blog post, tweeting that you're going to write a blog post, reading articles about how best to word your blog posts, watching some YouTube videos as inspiration, etc.

I think the advice here is an anti procrastination advice: do the thing, don't just think about doing the thing.