Neither the author of the GPT from scratch post, nor eclectic29 who recommended it above did ever promise that the post is about building LLMs from the ground up. That was the original post.
The GPT from scratch post explains, from the ground up, ground being numpy, what calculations take place inside a GPT model.
Your resource is really bad.
"We'll then load the trained GPT-2 model weights released by OpenAI into our implementation and generate some text."