How is the submitted article related to the headline? There's no claim of a "24hr notice" there, just that new sponsorships aren't being accepted.
First, editorializing the submission titles is against HN policies. Second, it'd let us see the actual communication from Vercel rather than a paraphrase.
And it's not so much about proof, it's about the details. For example the $300/month discount for a much longer transition period seems like pretty relevant context.