A much more recent comment from dang asked people to logout if they could when HN was under stress as it would make it faster for the user: https://news.ycombinator.com/item?id=38310213
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On Feb 28, 2023:
> Hi sph
> Yes, you ran into HN's anti-bot software, which blocked your IP. Sorry! Our intention is definitely not to block legit users, but we have to be somewhat aggressive about detecting bots because we don't have much performance to spare.
> I've unblocked your IP. If you browse HN while logged in, that should immunize you against this happening again. Also, if it ever does happen again, you can unban your IP as described at https://news.ycombinator.com/newsfaq.html. But you have to do that from a different IP address, of course.
> Let us know if you have any further trouble,
> Daniel (dang)
Emphasis mine.
But being logged out is more efficient for cached responses. The more load the site is under, the more this pays off.
It makes sense that they're both true - it's not a case of which is more recent, it's what problem they're solving.