wpgraft never reads Elementor’s data. There is no exporter, no importer and no shortcode translator anywhere in this, by design, because those are the parts that break. wpgraft reads the page as your browser rendered it: the real elements and the real computed styles on each one, at every breakpoint you ask for. It then rebuilds that as Gutenberg’s own native elements, with the styles written into Gutenberg’s own fields. Nothing that arrives depends on Elementor still existing.
Leaving Elementor for core blocks is the move people make to stop depending on a page builder at all, and the reason it stalls is that deactivating Elementor turns every page into a field of shortcodes. wpgraft avoids that completely: it never touches the Elementor page. It reads what Elementor rendered and builds the same design out of core WordPress blocks on a new page, which will still open in ten years on a WordPress with no page builder installed.