Many of the best writers out there were prolific. And there are innumerable bad writers who barely write at all.
Writing is an iterative process. I'm skeptical of advice about slowing down writing intentionally. I've found writing more and editing more improves my writing more than slower, more deliberate writing, particularly since it's less likely to happen.
To take liberties with your statement, I'd paraphrase this as "writing is work." I too agree with your skepticism of the article, and I'd argue it's because the platonic ideal of thinking before acting isn't actually how humans think.
Humans fundamentally do, and this action provides the ingredients from which to construct thought. Good writers produce lots of bad writing which allows them to reflect on their mistakes or identify the special subset of their writing that was good.
There's a point at which slowing down gives diminishing returns in my experience. I'm a music composer and I had to learn that the hard way. Sometimes my first ideas end up being good enough already, or even better than previous/future ideas that I had iterated a lot on. I also found that working for too long on a piece can potentially make it worse than previous iterations eventually.
Though it's also true that the last photo is also much more frequent. If I took 20 photos of something, I'd say I use either the first or last photo taken probably 1/3 of the time.