Nightfall's only training statement covers Google Workspace data. What it does with everything else isn't addressed.
“Google Workspace APIs accessed through our services are not used for developing, improving, or training our generalized artificial intelligence ("AI") or machine learning ("ML") models.”
Paste this where the card should sit. It is the live verdict: if the grade changes, the card changes. It loads nothing from anywhere but this site and sets no cookie.
Editors that support oEmbed (WordPress, Ghost, Substack and most newsroom systems) can paste the entry's address instead, https://isittrainingonme.com/app/nightfall/, and get the same card.