Thanks for the feedback blabla_bingo, I see the error. Yes, this is a mistake.
Here’s a working query for that example:
SELECT m.product_id, m.latest, MAX(b1.bug_id) AS latest_bug_id
FROM Bugs b1
JOIN BugsProducts p USING (bug_id)
JOIN (
SELECT product_id, MAX(date_reported) AS latest
FROM Bugs b2 JOIN BugsProducts USING (bug_id)
GROUP BY product_id
) m
ON (b1.date_reported = m.latest AND p.product_id = m.product_id)
GROUP BY m.product_id, m.latest;
I’ll try to get this correction into the next printing of the book.