How Extract images from PDF works
Extract images from PDF pulls the original embedded images out of a PDF and saves them as separate PNG files, the actual photos, logos and scans stored inside the document, at their embedded resolution.
This is not the same as rendering pages to pictures: if you want a PNG or JPG of how each whole page looks, use PDF to images instead. Extract images recovers the individual graphics that were placed in the file, at their embedded resolution, since extraction never upscales or re-renders.