Firstly, TFA has a bright red banner describing the opt-out mechanism. It's probably the second most attention-grabbing element on the page, after the countdown. Secondly, initially Google didn't mention any plans for an opt-out at all[1]. That was was only ceded after pushback[2].
[1]: https://web.archive.org/web/20260312134021/https://developer...
[2]: https://web.archive.org/web/20260328133800/https://developer...