Are you talking about https://news.ycombinator.com/item?id=45955996 ?

They were not confused, they were specifically talking about the distinction of 'certified' and how it applies to this article.

Colloquially, people commonly understand that "pre-owned" means "used".

This is different than people shortening their language while concurrently understanding the distinction.

How would anyone presume a warranty based off of the terms used or pre-owned? There's not an industry standard warranty that correlates to these terms. Anyone who's curious about a warranty would be told the terms of the warranty are anyway regardless of whether it was called it pre-owned or used.