It was indeed LaTeX. The ACM format creates a 1" box at the bottom of the first column which contains the copyright information. The copyright information on the authors' version (yes, I see the typo in the document now) doesn't take up much space so there's a lot of white space.

The block quote itself is just \begin{quote} ... \end{quote}.

The published version looks like this https://imgur.com/puBzzdZ

Hmm, I was going to say it was LaTeX, and that for all it's strengths, it always did strange things with boxes interacting with pagebreaks.

But there's nothing so bad that publisher's addon packages, and standards can't make worse.