Not sure if I am buying that excuse. I think they want to nudge people to make accounts and login. Really shady in case of Github and many other sides that are successful because of user content in my opinion.
Ironically, that makes the scraped copies more useful because they aren't truncated (at least for older pages) and I can actually get all the content. I wonder if that might be at least why Google seems to be giving them more weight in search result rankings.