I have a test domain that I prevent Google from indexing. DN Protect’s tool says the domain is banned.
The tool also interprets “Current status No available data” as “potentially dangerous”, which is ridiculous.
I would not rely on these reports when making a purchase decision. But don’t use 3rd-party SEO metrics of any kind, as far as I am concerned, as they are only automated opinions and don’t provide any insight into whether search engines trust a domain.