Yes, Mistral it was indeed. I share most of your skepticism, but their website does claim the engine(s) can run on unleaded mogas. Of course the www is a very tolerant medium, even more tolerant than paper - and no sheet of paper has ever protested the untruths written on it.
As always, we have to wait and see what turns up eventually - if anything ever does.
Unmatched flexibility in fuelling options: multi-fuel, MISTRAL engines works on avgas, unleaded mogas, mixtures thereof as well as ethanol-blended fuel