Quite right, PDF is mostly a 'flattened' subset of the PostScript format containing tokenised and interpreted data generated from the PostScript code, plus the subset of assets such as fonts that are actually used, in a bundle structure.

It also has some optimisations for it's specific use case, such as that individual pages are completely described independently, whereas in PostScript the code generating any page can affect the content of any succeeding page. This is why in PDF files you can easily re-order pages or efficiently jump directly to and render any page.