In the Google quote you link to, Google is not contacting your page. Rather, Google will index pages that are only linked to, which it has never crawled, and will serve up those pages if the link text matches your query. That's how you get those search results where the snippet is "A description of this page has been blocked by robots.txt" or similar.

There's a somewhat related issue where to ensure your site never exists in Google, you actually need to allow it to be crawled, because the standard for that is a "<meta name=noindex ...>" tag, and in order to see the meta noindex, the search engine has to fetch the page.

And the original point of my comment was that doing this is extremely rude and not appropriate, not that it couldn't be done or that others weren't doing it.

Feel free to send any request to any server you want, it is certainly up to them to decide whether or not to serve it, but that doesnt absolve you of guilt from scraping someone's site when they explicitly ask you not to.

Please don't conflate "extremely rude", "not appropriate", and "guilt". Two of these are subjective opinions about what constitutes good citizenship. The last one is a legal determination that has the potential to deprive an individual of both his money and liberty. We're discussing whether these behaviors should be legal, not whether they are necessarily polite.

I never did.

You are posting in a comment thread underneath my reply about rudeness and impoliteness, ironically being somewhat rude telling me off about what not to conflate when it was never what I said.

Google will put forbidden pages in its index. It doesn't scrape them. (The URL to the page exists even without visiting the page.)