The 24hr notice is mentioned by OP in their comment: https://news.ycombinator.com/item?id=40682720
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.