wpgraft never reads Oxygen’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 Instatic’s own native elements, with the styles written into Instatic’s own fields. Nothing that arrives depends on Oxygen still existing.
This move crosses platforms: Oxygen is WordPress, Instatic is a CMS you run on your own server, with a publisher that prints plain HTML and CSS. There is no plugin on either side. The copy goes into Instatic’s Site editor through Instatic’s own Import HTML, the same door its Paste HTML here… uses. Your Oxygen page stays where it is; nothing is migrated away from it.