Thing is, you have to start doing the thing to figure out what things you need to do the thing.

Well, to really know how things would pan out, you have to indeed do the thing.

And it happens that people will procrastinate with preparation. But as someone who does not and is fast at doing things I can tell you that if I want something done really fast preparation will be a good chunk of a projects time. If I want to toy around and the project doesn't matter that much, just doing the thing may do the trick.

Now the advice on that site aims to get people started with the actual work part and tries to do so by telling you preparation doesn't matter. That is not true. But it is true that people prepare forever because they are afraid to cross the threshold where they start translating grand ideas into concrete, protentially flawed reality. That means actually good advice would deal with the question where this fear comes from, how to address it and how to notice you have been preparing too long.

If you want to build a house, drawing the plans and finding the right location where to put said house is part of building a house. Or you could just mash bricks on top of each other in your backyard and then realize you forgot the foundation.

Yes. Also, attempting to do the thing and failing is indeed doing the thing. (although you may only know in retrospect)