It does respect robots.txt, but that doesn't mean it won't index the content hidden behind robots.txt. That file is context dependent. Here's an example.

Site X has a link to sitemap.html on the front page and it is blocked inside robots.txt. When Google crawler visits site X it will first load robots.txt and will follow its instructions and will skip sitemap.html.

Now there's site Y and it also links to sitemap.html on X. Well, in this context the active robots.txt file is from Y and it doesn't block anything on X (and it cannot), so now the crawler has the green light to fetch sitemap.html.

This behaviour is intentional.

Lol. And they'll delist you. Unless you're really important, good luck with that.

robots.txt

Disallow: /some-page.html

If you disallow a page in robots.txt Google won't crawl the page. Even when Google finds links to the page and knows it exists, Googlebot won't download the page or see the contents. Google will usually not choose to index the URL, however that isn't 100%. Google may include the URL in the search index along with words from the anchor text of links to it if it feels that it may be an important page.

It's naive to assume that google crawlers respect robot.txt.