The fact that he didn't spend pages talking about it is not the issue, but that he didn't when there's a large amount of case law that interprets the anti-circumvention clause of the DMCA completely differently. The second update to the story provides a more likely reasoning for the lack of analysis:
"Update: New York Law School's James Grimmelmann emails to suggest an alternative explanation or the shortness of the judge's DMCA analysis. He notes that the plaintiffs focused their arguments on the trafficking provisions of the DMCA, but ignored the circumvention provisions. Since the plaintiffs didn't raise the circumvention issue, Judge Marshall didn't need to address it. He dismissed the lawsuit without prejudice, so Ambrose can amend its complaint and try again."
"Update: New York Law School's James Grimmelmann emails to suggest an alternative explanation or the shortness of the judge's DMCA analysis. He notes that the plaintiffs focused their arguments on the trafficking provisions of the DMCA, but ignored the circumvention provisions. Since the plaintiffs didn't raise the circumvention issue, Judge Marshall didn't need to address it. He dismissed the lawsuit without prejudice, so Ambrose can amend its complaint and try again."