wpgraft reads the page as your browser rendered it, the real elements and the real computed styles, at every breakpoint you ask for, and rebuilds it as Gutenberg’s own native elements with the styles in Gutenberg’s own fields. It does not care that a language model wrote the HTML, and it does not care what framework the page was built with: by the time wpgraft looks, all of that has already become computed styles.
A page Claude writes is one clean self-contained HTML document, which is close to the best possible input for a converter. What it is not is editable by anyone who does not read HTML. wpgraft rebuilds it as core WordPress blocks, with no page builder involved and editable by whoever owns the site.