I would note that “artificial hybrid” doesn’t necessarily mean “horticultural hybrid” on POWO - I raised a flag a while ago to get × Reyllopia conollyana added to iNat and I was told to email them to ask them to accept it as naturally occuring.
POWO describes this species as an “artificial hybrid” - it’s a hybrid with the globally-invasive Japanese knotweed, so good luck finding anyone growing it deliberately, and the Russian-vine / mile-a-minute, a maybe-also-invasive-in-Western-Europe popular garden plant. Their hybrid is known to self-sow in Western Europe - plants have been found wild in Belgium and the UK, but it’s very rare.
I emailed POWO about that “artificial hybrid” tag and I was told that it IS artificial because it cannot possibly occur in the plant’s native ranges (the former to Japan, the latter to Central Asia - no overlap at all), but that doesn’t mean it can’t occur ‘naturally’ where both species are present such as Western Europe.