In 2021 Bing, Yandex, Seznam.cz, and (later, in 2023) Naver ended up implementing a standard where you can notify one search engine of a page update and the other participating search engines are also notified [1, 2, 3].

[1]: https://www.indexnow.org/

[2]: https://www.bing.com/indexnow

[3]: https://blogs.bing.com/webmaster/october-2021/IndexNow-Insta...

>The best explanation I can come up with is that a failure to notify them of a change makes them look bad when their search results are out of date. Especially if the failures are malicious, fitting in with the general theme of the article.

Should be easy to crosscheck the reliability of update notifications by doing a little bit of polling too.