It’s in the document they link pretty early on. You can argue they could make it more obvious in the blog I guess but that’s flimsy IMO and calling it hidden isn’t accurate
Fair enough. Yes, it is in the linked document. I agree that's sufficient. I was responding to people suggesting that Mozilla didn't need to declare this at all.
They link to the full document which lists their VPN subscriber count near the top of the about Mozilla section.