What Google announced
The proposal would let website owners express training preferences to multiple participating providers through robots.txt. Google plans to treat an opt-out through the shared signal as a Google-Extended opt-out when the file contains no explicit Google-Extended instruction.
Which settings to review today
Document the current Google-Extended rule, the Search generative AI setting in Search Console and who signs off on both. They cover different uses. On 30 October, Google was aiming to support the new signal in 2027. The announcement alone cannot establish when it is active or which other providers honour it.