While the Zyppy article is interesting in that it has statistics about the title rewriting, the Google guide on writing proper titles is more relevant to all of us who maintain websites affected by this. Thanks for linking it.

The ideal article would be something like "Google rewrites your titles in search results because your titles suck."

The Google guide does well to explain why some titles are rewritten, such as having duplicate titles across multiple pages, making it impossible to differentiate between pages that show up in the same set of search results.

In other words, Google's policy is that the search result isn't showing the page title, it's showing Google's short description of the page. If Google thinks your page title is an adequate description it might use that, otherwise it will write its own.

(edit: and Google has enough self-importance to advise you to write your title as if it were a short description, to make their job easier)

TIL that indexing and crawling are different, and robots.txt prevents Google from crawling but not indexing.