Hm... I was definitely under the impression that it is generating SVGs natively, and that was consistent with its output and its recent upgrades like good text rendering, and I'm fairly sure I've said as much to the CEO and not been corrected... But I don't offhand recollect a specific reference where they say unambiguously that it's a SVG generator rather than vectorizer(raster), so maybe I'm wrong about that.
For me its based on that vector generation is much harder than raster, recraft has raised just over $10M (not that much in this space), and their api has no direct vector generation.