Not sure that is fair? The difference seems to be the data is squarely in your own DB. You can use their SaaS for validation. You might pay for something (surprise?).
It would be pulling in another SaaS, what isn't fair?
It actually sounds like an interesting service in my opinion, but it is another SaaS that is giving me an API for a form handler that I could otherwise host myself.
Personally I wouldn't see the use case of using your own DB as helpful, if you already have your own database the odds that you aren't hosting APIs as well seems low.